title
CS50 2021 in HDR - Lecture 8 - HTML, CSS, JavaScript

description
This is CS50, Harvard University's Introduction to the intellectual enterprises of computer science and the art of programming. Enroll for free at https://cs50.edx.org/. Slides, source code, and more at https://cs50.harvard.edu/x. Playlist at https://www.youtube.com/playlist?list=PLhQjrBD2T383f9scHRNYJkior2VvYjpSL. TABLE OF CONTENTS 00:00:00 - Introduction 00:01:17 - The Internet 00:05:08 - Routers 00:08:40 - TCP/IP 00:13:50 - Fragmentation 00:17:52 - DNS 00:19:37 - HTTP Requests and Responses 00:39:27 - Pep Squad 00:42:58 - HTML 00:45:45 - http-server 00:47:29 - Tags and Attributes 00:53:51 - HTML Validation 00:55:01 - paragraphs.html 00:57:26 - headings.html 00:59:02 - list.html 01:01:14 - table.html 01:04:14 - image.html 01:06:57 - video.html 01:10:30 - link.html 01:14:12 - responsive.html 01:19:20 - URL Parameters 01:25:50 - home.html 01:27:40 - Semantic Tags 01:28:08 - Style Attributes 01:32:19 - CSS 01:35:40 - CSS Classes 01:37:00 - Linking CSS 01:39:15 - ID Selectors 01:40:24 - Developer Tools 01:47:21 - Pseudo-classes 01:52:27 - Frameworks 02:05:48 - JavaScript 02:10:40 - onsubmit 02:12:36 - querySelector 02:14:31 - Event Listeners 02:17:16 - Anonymous Functions 02:18:57 - JavaScript Examples 02:21:32 - geolocation.html 02:22:42 - This was CS50 *** This is CS50, Harvard University's introduction to the intellectual enterprises of computer science and the art of programming. *** HOW TO SUBSCRIBE http://www.youtube.com/subscription_center?add_user=cs50tv HOW TO TAKE CS50 edX: https://cs50.edx.org/ Harvard Extension School: https://cs50.harvard.edu/extension Harvard Summer School: https://cs50.harvard.edu/summer OpenCourseWare: https://cs50.harvard.edu/x HOW TO JOIN CS50 COMMUNITIES Discord: https://discord.gg/cs50 Ed: https://cs50.harvard.edu/x/ed Facebook Group: https://www.facebook.com/groups/cs50/ Faceboook Page: https://www.facebook.com/cs50/ GitHub: https://github.com/cs50 Gitter: https://gitter.im/cs50/x Instagram: https://instagram.com/cs50 LinkedIn Group: https://www.linkedin.com/groups/7437240/ LinkedIn Page: https://www.linkedin.com/school/cs50/ Medium: https://cs50.medium.com/ Quora: https://www.quora.com/topic/CS50 Reddit: https://www.reddit.com/r/cs50/ Slack: https://cs50.edx.org/slack Snapchat: https://www.snapchat.com/add/cs50 SoundCloud: https://soundcloud.com/cs50 Stack Exchange: https://cs50.stackexchange.com/ TikTok: https://www.tiktok.com/@cs50 Twitter: https://twitter.com/cs50 YouTube: http://www.youtube.com/cs50 HOW TO FOLLOW DAVID J. MALAN Facebook: https://www.facebook.com/dmalan GitHub: https://github.com/dmalan Instagram: https://www.instagram.com/davidjmalan/ LinkedIn: https://www.linkedin.com/in/malan/ Quora: https://www.quora.com/profile/David-J-Malan TikTok: https://www.tiktok.com/@davidjmalan Twitter: https://twitter.com/davidjmalan *** CS50 SHOP https://cs50.harvardshop.com/ *** LICENSE CC BY-NC-SA 4.0 Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International Public License https://creativecommons.org/licenses/by-nc-sa/4.0/ David J. Malan https://cs.harvard.edu/malan malan@harvard.edu

detail
{'title': 'CS50 2021 in HDR - Lecture 8 - HTML, CSS, JavaScript', 'heatmap': [{'end': 1550.881, 'start': 1462.324, 'weight': 0.765}, {'end': 2236.608, 'start': 2144.687, 'weight': 0.735}, {'end': 2842.824, 'start': 2749.196, 'weight': 1}, {'end': 5162.615, 'start': 4987.339, 'weight': 0.85}], 'summary': 'Covers topics including web programming, data routing, tcp/ip and dns protocols, http headers, html fundamentals and styling, video tag creation, front-end development with html, css, and javascript, using bootstrap and javascript for web development, and javascript interaction and dom manipulation, providing a comprehensive overview of key concepts and practical demonstrations.', 'chapters': [{'end': 552.525, 'segs': [{'end': 225.529, 'src': 'embed', 'start': 194.57, 'weight': 0, 'content': [{'end': 197.232, 'text': 'How would you describe it? Big storage.', 'start': 194.57, 'duration': 2.662}, {'end': 197.432, 'text': 'DAVID J.', 'start': 197.252, 'duration': 0.18}, {'end': 198.233, 'text': 'OK, big storage.', 'start': 197.432, 'duration': 0.801}, {'end': 205.179, 'text': "And indeed, that's how the cloud is described, which is kind of an abstraction, if you will, for a whole lot of wires and cables and hardware.", 'start': 198.253, 'duration': 6.926}, {'end': 208.181, 'text': 'And the internet, other formulations of the term.', 'start': 206.139, 'duration': 2.042}, {'end': 216.223, 'text': 'How else? OK, a bunch of data that we can all reach by way of being interconnected somehow with wires or wirelessly.', 'start': 208.902, 'duration': 7.321}, {'end': 219.145, 'text': 'And so really, the internet, too, is a hardware thing.', 'start': 216.543, 'duration': 2.602}, {'end': 225.529, 'text': "There's a whole lot of servers out there that are somehow interconnected via physical cables, via internet service providers,", 'start': 219.185, 'duration': 6.344}], 'summary': 'The cloud is described as big storage, an abstraction for interconnected data reached by wires or wirelessly.', 'duration': 30.959, 'max_score': 194.57, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg194570.jpg'}], 'start': 11.303, 'title': 'Web programming and data routing', 'summary': 'Covers the evolution of cs50 to web programming, including the shift from gui to textual interfaces, and delves into the fundamentals of the internet and its networks. it also explains the role of routers in data routing across networks, the process of sending data packets, and the use of protocols such as tcpip in computer communication.', 'chapters': [{'end': 300.336, 'start': 11.303, 'title': 'Cs50 week 8: exploring web programming', 'summary': 'Discusses the evolution of cs50 from scratch to web programming, explaining the shift from gui to textual interfaces, and delving into the fundamentals of the internet and its interconnected networks.', 'duration': 289.033, 'highlights': ["CS50's evolution from Scratch to web programming The chapter highlights the transition from Scratch to web programming, emphasizing the shift in interfaces from GUI to textual, and the introduction of web elements.", "Explanation of the internet's interconnected networks The transcript explains the interconnected nature of the internet, detailing how networks of networks create the internet and providing a historical perspective from ARPANET to the present day.", 'Fundamentals of the internet and its hardware components The chapter delves into the hardware components of the internet, describing it as a network of servers interconnected via physical cables, internet service providers, and wireless connectivity.']}, {'end': 552.525, 'start': 300.456, 'title': 'Understanding routers and data routing', 'summary': 'Explains the fundamental role of routers in routing data across networks, the process of sending data packets through routers, and the use of protocols such as tcpip in computer communication.', 'duration': 252.069, 'highlights': ['Routers serve as the essential infrastructure for routing data across networks, with each router determining the path for data transmission. The chapter emphasizes the critical role of routers in network infrastructure, highlighting their responsibility for determining the path of data transmission, whether within a local network or across different geographical locations.', 'The process of sending data from one point to another involves handing the data to the nearest local router, which then navigates the data across multiple routers until it reaches the intended destination. The explanation of the process of sending data involves handing it to the nearest local router, which then navigates the data across multiple routers until it reaches the intended destination, showcasing the complexity of data transmission across different geographical locations.', 'TCPIP, a set of protocols, plays a crucial role in computer communication, providing the rules and conventions for intercommunication between devices. The chapter introduces TCPIP as a set of protocols that form the foundation for computer communication, highlighting its significance in providing the rules and conventions for intercommunication between devices in modern networks.']}], 'duration': 541.222, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg11303.jpg', 'highlights': ["CS50's evolution from Scratch to web programming, emphasizing the shift in interfaces from GUI to textual and the introduction of web elements.", 'The interconnected nature of the internet, detailing how networks of networks create the internet and providing a historical perspective from ARPANET to the present day.', 'The hardware components of the internet, describing it as a network of servers interconnected via physical cables, internet service providers, and wireless connectivity.', 'Routers serve as the essential infrastructure for routing data across networks, with each router determining the path for data transmission.', 'The process of sending data involves handing it to the nearest local router, which then navigates the data across multiple routers until it reaches the intended destination, showcasing the complexity of data transmission across different geographical locations.', 'TCPIP, a set of protocols, plays a crucial role in computer communication, providing the rules and conventions for intercommunication between devices.']}, {'end': 1745.063, 'segs': [{'end': 747.248, 'src': 'embed', 'start': 717.484, 'weight': 0, 'content': [{'end': 720.127, 'text': "There's all of these different functions on the internet nowadays.", 'start': 717.484, 'duration': 2.643}, {'end': 727.854, 'text': "And so when Brian receives that envelope, how does he know it's an email versus versus a web page,", 'start': 720.648, 'duration': 7.206}, {'end': 731.536, 'text': 'versus a Skype call versus something else altogether?', 'start': 727.854, 'duration': 3.682}, {'end': 738.28, 'text': 'Well, it turns out that we can look at the other part of this acronym the TCP in TCP IP.', 'start': 731.897, 'duration': 6.383}, {'end': 742.843, 'text': 'And what TCP allows us to do, for instance, is specify a couple of things.', 'start': 738.62, 'duration': 4.223}, {'end': 747.248, 'text': 'the type of service whose data is in this envelope.', 'start': 743.843, 'duration': 3.405}], 'summary': 'Tcp ip helps specify the type of service for data transmission over the internet.', 'duration': 29.764, 'max_score': 717.484, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg717484.jpg'}, {'end': 926.263, 'src': 'embed', 'start': 898.297, 'weight': 8, 'content': [{'end': 903.959, 'text': 'Like, if you were implementing this, chopping up this picture of a cat into four parts intuitively,', 'start': 898.297, 'duration': 5.662}, {'end': 908.401, 'text': 'what might you want to put virtually on the outside of this envelope now? Yeah.', 'start': 903.959, 'duration': 4.442}, {'end': 910.951, 'text': 'the order of them somehow.', 'start': 909.85, 'duration': 1.101}, {'end': 916.075, 'text': 'So probably something like part 1 of 4, part 2 of 4, part 3 of 4, and so forth.', 'start': 911.031, 'duration': 5.044}, {'end': 919.218, 'text': "So I'm going to write one more thing in the memo line of the envelope here.", 'start': 916.315, 'duration': 2.903}, {'end': 926.263, 'text': "I put some kind of sequence number that's just a little bit of a clue to Brian to know in what order to reassemble these things.", 'start': 919.638, 'duration': 6.625}], 'summary': 'Suggests organizing picture parts into sequence numbers for reassembly.', 'duration': 27.966, 'max_score': 898.297, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg898297.jpg'}, {'end': 1289.082, 'src': 'embed', 'start': 1248.897, 'weight': 3, 'content': [{'end': 1251.739, 'text': 'So this is a distinction now between the internet and the web.', 'start': 1248.897, 'duration': 2.842}, {'end': 1258.585, 'text': 'The internet is really like the low-level plumbing, all of the cables, all of the technology that just moves packets from left to right,', 'start': 1251.799, 'duration': 6.786}, {'end': 1259.986, 'text': 'right to left, top to bottom.', 'start': 1258.585, 'duration': 1.401}, {'end': 1262.548, 'text': 'that gets data from point A to point B.', 'start': 1259.986, 'duration': 2.562}, {'end': 1270.174, 'text': 'You can do anything you want on top of that internet nowadays, email, and web and video and chat and gaming and all of that.', 'start': 1262.548, 'duration': 7.626}, {'end': 1278.157, 'text': 'So HTTP, or the web, is just one application that is conceptually built on top of the internet.', 'start': 1270.214, 'duration': 7.943}, {'end': 1282.819, 'text': 'Once you take for granted that there is an internet, you can do really interesting things with it, just like in our physical world.', 'start': 1278.297, 'duration': 4.522}, {'end': 1289.082, 'text': 'Once you have electricity, you can just assume you can do really interesting things with that, too, without even knowing or caring how it works.', 'start': 1282.939, 'duration': 6.143}], 'summary': 'The internet is the infrastructure, while the web is one application built on top, enabling various activities.', 'duration': 40.185, 'max_score': 1248.897, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1248897.jpg'}, {'end': 1386.318, 'src': 'embed', 'start': 1358.64, 'weight': 1, 'content': [{'end': 1364.524, 'text': 'It can have slash path, where path is just a word or multiple words that sort of describe a longer part of the URL.', 'start': 1358.64, 'duration': 5.884}, {'end': 1369.368, 'text': "That path could actually be a specific file, we'll see, like something called file.html.", 'start': 1364.885, 'duration': 4.483}, {'end': 1370.769, 'text': 'More on HTML in just a bit.', 'start': 1369.508, 'duration': 1.261}, {'end': 1374.151, 'text': 'Or it can even be slash folder, maybe with another slash.', 'start': 1371.169, 'duration': 2.982}, {'end': 1376.853, 'text': 'Or maybe it can be slash folder slash file.html.', 'start': 1374.271, 'duration': 2.582}, {'end': 1380.335, 'text': 'Now, these days, Safari and even Chrome to some extent,', 'start': 1377.253, 'duration': 3.082}, {'end': 1386.318, 'text': 'and other browsers are in the habit of trying to hide more and more of these details from you and me.', 'start': 1380.335, 'duration': 5.983}], 'summary': 'Url can have slash path, file.html, folder, and browser behavior.', 'duration': 27.678, 'max_score': 1358.64, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1358640.jpg'}, {'end': 1424, 'src': 'embed', 'start': 1398.925, 'weight': 2, 'content': [{'end': 1404.448, 'text': "a specific file and or folder on the web server on which you're programming.", 'start': 1398.925, 'duration': 5.523}, {'end': 1408.67, 'text': "All right, what's this? Example.com, this is the domain name as we described it earlier.", 'start': 1404.628, 'duration': 4.042}, {'end': 1412.513, 'text': 'Example.com is the so-called domain name.', 'start': 1410.271, 'duration': 2.242}, {'end': 1417.516, 'text': 'This whole thing, www.example.com, is the fully qualified domain name.', 'start': 1412.853, 'duration': 4.663}, {'end': 1424, 'text': 'And what the WW is referring to is specifically the name of a specific server in that domain.', 'start': 1417.916, 'duration': 6.084}], 'summary': 'The transcript discusses domain names and web servers.', 'duration': 25.075, 'max_score': 1398.925, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1398925.jpg'}, {'end': 1550.881, 'src': 'heatmap', 'start': 1462.324, 'weight': 0.765, 'content': [{'end': 1463.645, 'text': 'top-level domain.', 'start': 1462.324, 'duration': 1.321}, {'end': 1467.587, 'text': 'Probably know that .com means commercial, although anyone can buy it these days.', 'start': 1463.865, 'duration': 3.722}, {'end': 1469.408, 'text': '.org is similar, .net.', 'start': 1467.727, 'duration': 1.681}, {'end': 1471.229, 'text': 'Some of them are a bit restricted.', 'start': 1470.029, 'duration': 1.2}, {'end': 1472.97, 'text': '.mil is just for the US military.', 'start': 1471.589, 'duration': 1.381}, {'end': 1475.612, 'text': '.edu is just for accredited educational institutions.', 'start': 1473.25, 'duration': 2.362}, {'end': 1481.855, 'text': 'But there are hundreds, if not more, top-level domains nowadays, some more popular than others.', 'start': 1475.892, 'duration': 5.963}, {'end': 1485.177, 'text': "CS50's tools, for instance, use CS50.io.", 'start': 1481.915, 'duration': 3.262}, {'end': 1488.139, 'text': 'IO sort of connotes input-output.', 'start': 1485.938, 'duration': 2.201}, {'end': 1495.304, 'text': 'It actually belongs, though, to a small island nation, a country whose country code is .io.', 'start': 1488.499, 'duration': 6.805}, {'end': 1500.449, 'text': 'And you see other two-letter top-level domains that are country-specific.', 'start': 1495.625, 'duration': 4.824}, {'end': 1505.353, 'text': 'indeed, something uk, something jp and the like typically refer to countries.', 'start': 1500.449, 'duration': 4.904}, {'end': 1510.618, 'text': 'But some of them have been rather co-opted, .tv as well, because they have these meanings in English as well.', 'start': 1505.393, 'duration': 5.225}, {'end': 1517.664, 'text': "Lastly, this is what we'll call the protocol that specifies how the server uses this URL to get data from point A to point B.", 'start': 1511.179, 'duration': 6.485}, {'end': 1522.547, 'text': "So what is inside of this envelope? Let's now start poking around a little bit more.", 'start': 1518.425, 'duration': 4.122}, {'end': 1529.792, 'text': "What is inside of this envelope? It's essentially, for our purposes today, one of two verbs, either get or post.", 'start': 1522.948, 'duration': 6.844}, {'end': 1534.254, 'text': 'And if any of you have dabbled with HTML or made your own website, you might have seen some of these terms before.', 'start': 1530.012, 'duration': 4.242}, {'end': 1540.718, 'text': 'But these two verbs describe just how to send information from you to the server.', 'start': 1534.674, 'duration': 6.044}, {'end': 1543.179, 'text': 'Long story short, more on this next week.', 'start': 1541.438, 'duration': 1.741}, {'end': 1545.659, 'text': 'Get means put any user input in the URL.', 'start': 1543.439, 'duration': 2.22}, {'end': 1550.881, 'text': "Post means hide it, so that things you're searching for credit card numbers, you're typing in,", 'start': 1546.179, 'duration': 4.702}], 'summary': "Explains top-level domains, including .com, .org, .net, .mil, .edu, and country-specific domains. also introduces the use of verbs like 'get' and 'post' for sending information to servers.", 'duration': 88.557, 'max_score': 1462.324, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1462324.jpg'}], 'start': 552.805, 'title': 'Tcp/ip and dns protocols', 'summary': 'Provides an overview of tcp and ip protocols, including their roles in addressing and routing data packets, as well as the significance of dns in converting domain names to ip addresses. it also emphasizes the use of port numbers to identify different types of services and discusses the structure of urls and the http protocol.', 'chapters': [{'end': 824.777, 'start': 552.805, 'title': 'Tcp/ip protocol overview', 'summary': 'Explains the tcp and ip protocols, including their roles in addressing and routing data packets, the structure and format of ip addresses, and the use of port numbers to identify different types of services, with an emphasis on the scalability of ip addresses and the standardization of port numbers.', 'duration': 271.972, 'highlights': ['IP addresses use 32 bits or 4 bytes, allowing for 4 billion possible addresses, but due to the increasing number of devices, version 6 of IP, using 128 bits, is being used to accommodate the growing number of devices. IP addresses use 32 bits or 4 bytes, providing 4 billion possible addresses, but the use of version 6, with 128 bits, allows for a significantly larger number of addresses to handle the increasing number of devices.', 'The role of TCP in TCP/IP is to specify the type of service being sent, which is indicated by a numeric identifier known as a port number, such as port 80 for web traffic and 443 for encrypted web traffic (HTTPS). TCP specifies the type of service being sent with a numeric identifier known as a port number, e.g., port 80 for web traffic and 443 for encrypted web traffic (HTTPS).', 'Port numbers are standardized and used to differentiate various types of services, e.g., port 25, 465, and 587 for email and port 80 and 443 for web traffic, with these numbers being essential for configuring email clients like Outlook or Gmail. Port numbers are standardized and differentiate various services, e.g., port 25, 465, and 587 for email, and port 80 and 443 for web traffic, essential for configuring email clients like Outlook or Gmail.']}, {'end': 1145.137, 'start': 824.937, 'title': 'Tcp/ip and dns: enabling efficient data transmission', 'summary': 'Discusses the concept of tcp/ip, which allows for fair sharing of network bandwidth, guarantees delivery of data, and the significance of dns in converting domain names to ip addresses, with a mention of the alternative protocol udp.', 'duration': 320.2, 'highlights': ['TCP/IP ensures fair sharing of network bandwidth by timesharing interconnections across routers, allowing for efficient transmission of large files and implementation of fragmentation to temporarily split packets. TCP/IP allows for fair timesharing of interconnections across routers to prevent the monopolization of network bandwidth, facilitating efficient transmission of large files through the implementation of fragmentation.', 'The use of sequence numbers in TCP/IP packets enables guaranteed delivery of data, ensuring that all the packets are received in the correct order or none at all, distinguishing it from protocols like UDP that do not guarantee delivery. TCP/IP uses sequence numbers to guarantee delivery of data, ensuring that all packets are received in the correct order or none at all, distinguishing it from protocols like UDP that do not provide this guarantee.', 'The Domain Name System (DNS) plays a crucial role in converting domain names to IP addresses, allowing users to access websites using user-friendly domain names instead of numerical IP addresses, with DNS servers maintaining a comprehensive table of domain names and corresponding IP addresses. The Domain Name System (DNS) converts domain names to IP addresses, enabling users to access websites using user-friendly domain names, with DNS servers maintaining a comprehensive table of domain names and corresponding IP addresses.']}, {'end': 1745.063, 'start': 1145.137, 'title': 'Understanding dns, urls, and http', 'summary': 'Explains the purpose of dns servers, the structure of urls, and the http protocol, emphasizing how data is transferred and how servers respond to requests, and discusses the relationship between the internet and the web.', 'duration': 599.926, 'highlights': ["DNS servers translate domain names to IP addresses and vice versa, and translate fully qualified domain names to IP addresses. DNS servers' purpose is to translate domain names to IP addresses and vice versa, including fully qualified domain names, to enable communication over the internet.", 'HTTP is a protocol that standardizes how web browsers and web servers intercommunicate, and it specifies what kinds of messages go inside envelopes. HTTP standardizes the communication between web browsers and servers, specifying the content and format of the messages exchanged, facilitating the transfer of web content.', 'The distinction between the internet and the web is explained, with the internet being the low-level infrastructure for data transfer and the web being an application built on top of the internet. The internet is described as the foundational technology for data transfer, while the web is presented as an application built on top of the internet, allowing various functionalities like email, web, video, chat, and gaming to be implemented.']}], 'duration': 1192.258, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg552805.jpg', 'highlights': ['The use of version 6 of IP, with 128 bits, allows for a significantly larger number of addresses to handle the increasing number of devices.', 'TCP specifies the type of service being sent with a numeric identifier known as a port number, e.g., port 80 for web traffic and 443 for encrypted web traffic (HTTPS).', 'Port numbers are standardized and differentiate various services, e.g., port 25, 465, and 587 for email, and port 80 and 443 for web traffic, essential for configuring email clients like Outlook or Gmail.', 'TCP/IP allows for fair timesharing of interconnections across routers to prevent the monopolization of network bandwidth, facilitating efficient transmission of large files through the implementation of fragmentation.', 'TCP/IP uses sequence numbers to guarantee delivery of data, ensuring that all packets are received in the correct order or none at all, distinguishing it from protocols like UDP that do not provide this guarantee.', 'The Domain Name System (DNS) converts domain names to IP addresses, enabling users to access websites using user-friendly domain names, with DNS servers maintaining a comprehensive table of domain names and corresponding IP addresses.', "DNS servers' purpose is to translate domain names to IP addresses and vice versa, including fully qualified domain names, to enable communication over the internet.", 'HTTP standardizes the communication between web browsers and servers, specifying the content and format of the messages exchanged, facilitating the transfer of web content.', 'The internet is described as the foundational technology for data transfer, while the web is presented as an application built on top of the internet, allowing various functionalities like email, web, video, chat, and gaming to be implemented.']}, {'end': 2503.638, 'segs': [{'end': 1826.916, 'src': 'embed', 'start': 1796.713, 'weight': 1, 'content': [{'end': 1802.977, 'text': 'but because it throws away any history that I just did, so that every request is going to look like a brand new one.', 'start': 1796.713, 'duration': 6.264}, {'end': 1806.74, 'text': "And that's just useful diagnostically because we're always going to see fresh information.", 'start': 1803.278, 'duration': 3.462}, {'end': 1809.823, 'text': 'My browser is not going to remember what I previously already requested.', 'start': 1807.081, 'duration': 2.742}, {'end': 1817.168, 'text': "But I'm going to go up to View, Developer, Developer Tools, which is something that all of you have if you use Chrome.", 'start': 1810.563, 'duration': 6.605}, {'end': 1821.472, 'text': "And there's something analogous for Firefox and Edge and Safari and other browsers.", 'start': 1817.248, 'duration': 4.224}, {'end': 1824.354, 'text': 'Developer Tools is going to open up these tabs down here.', 'start': 1821.972, 'duration': 2.382}, {'end': 1826.916, 'text': "I don't really care what's new, so I'm going to close the bottom thing there.", 'start': 1824.514, 'duration': 2.402}], 'summary': 'Using developer tools in browsers for fresh diagnostic information.', 'duration': 30.203, 'max_score': 1796.713, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1796713.jpg'}, {'end': 1923.691, 'src': 'embed', 'start': 1895.105, 'weight': 2, 'content': [{'end': 1897.427, 'text': "And then I'm going to see a bit of diagnostic information.", 'start': 1895.105, 'duration': 2.322}, {'end': 1899.449, 'text': 'To an average person using the web.', 'start': 1897.807, 'duration': 1.642}, {'end': 1904.934, 'text': "they needn't care about this, just as you probably didn't care about it until right now, and even then perhaps not.", 'start': 1899.449, 'duration': 5.485}, {'end': 1910.399, 'text': 'But if I scroll down to Request Headers, you will see if I click View Source,', 'start': 1905.374, 'duration': 5.025}, {'end': 1915.423, 'text': 'Literally everything that was in the request my Mac just sent to harvard.edu.', 'start': 1910.979, 'duration': 4.444}, {'end': 1923.691, 'text': "Two of the lines are familiar, get slash http 1.1, host colon harvard.edu, and then other stuff that, for now, it's not that interesting for us.", 'start': 1915.784, 'duration': 7.907}], 'summary': 'Diagnostic information revealed in web request to harvard.edu.', 'duration': 28.586, 'max_score': 1895.105, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1895105.jpg'}, {'end': 2236.608, 'src': 'heatmap', 'start': 2144.687, 'weight': 0.735, 'content': [{'end': 2151.853, 'text': "So instead of getting back, for instance, something like OK or move permanently, what I've just gotten back quite simply is 404 not found.", 'start': 2144.687, 'duration': 7.166}, {'end': 2153.514, 'text': "Well, it turns out there's other.", 'start': 2152.213, 'duration': 1.301}, {'end': 2158.94, 'text': "types of status codes that you'll start to see over time as you start to program for the web.", 'start': 2153.914, 'duration': 5.026}, {'end': 2160.281, 'text': '200 is OK.', 'start': 2159.581, 'duration': 0.7}, {'end': 2162.003, 'text': '301 is moved permanently.', 'start': 2160.301, 'duration': 1.702}, {'end': 2165.587, 'text': '302, 304, 307 are all similar in spirit.', 'start': 2162.023, 'duration': 3.564}, {'end': 2168.471, 'text': "They're related to redirecting the user from one place to another.", 'start': 2165.607, 'duration': 2.864}, {'end': 2172.775, 'text': '401, 403, unauthorized or forbidden.', 'start': 2170.593, 'duration': 2.182}, {'end': 2177.52, 'text': "If you ever mess up your password or you try visiting a URL you're not supposed to look at.", 'start': 2173.155, 'duration': 4.365}, {'end': 2182.065, 'text': "you might see one of these codes indicating that you just don't have authorization for those.", 'start': 2177.52, 'duration': 4.545}, {'end': 2182.926, 'text': '404, not found.', 'start': 2182.085, 'duration': 0.841}, {'end': 2187.651, 'text': "418, I'm a teapot, was an April Fool's joke by the tech community years ago.", 'start': 2183.166, 'duration': 4.485}, {'end': 2189.252, 'text': '500 is bad.', 'start': 2188.331, 'duration': 0.921}, {'end': 2196.779, 'text': 'And unfortunately all of you are probably on a path now to creating HTTP 500 errors once next week we start writing code,', 'start': 2189.732, 'duration': 7.047}, {'end': 2198.18, 'text': 'because all of us are going to screw up.', 'start': 2196.779, 'duration': 1.401}, {'end': 2199.922, 'text': "We're going to have typos, logical errors.", 'start': 2198.2, 'duration': 1.722}, {'end': 2207.008, 'text': 'And this is on the horizon, just like seg faults were in the world of C, but solvable with the right skills.', 'start': 2200.482, 'duration': 6.526}, {'end': 2210.371, 'text': "503, service unavailable, means maybe the server's overloaded or something like that.", 'start': 2207.028, 'duration': 3.343}, {'end': 2214.154, 'text': "And there's other codes there, but those are perhaps some of the most common ones.", 'start': 2210.431, 'duration': 3.723}, {'end': 2218.497, 'text': 'Has anyone, we can get away with this here, less so in New Haven.', 'start': 2215.255, 'duration': 3.242}, {'end': 2229.964, 'text': 'Has anyone ever visited safetyschool.org? http://safetyschool.org.', 'start': 2218.877, 'duration': 11.087}, {'end': 2231.605, 'text': 'Dare we do this? Enter.', 'start': 2229.984, 'duration': 1.621}, {'end': 2233.886, 'text': 'Oh, look at that.', 'start': 2232.906, 'duration': 0.98}, {'end': 2236.608, 'text': 'Where did we end up? OK, so.', 'start': 2233.946, 'duration': 2.662}], 'summary': 'Http status codes indicate response and errors, such as 404 not found, 401 unauthorized, 500 bad, and 503 service unavailable.', 'duration': 91.921, 'max_score': 2144.687, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg2144687.jpg'}, {'end': 2236.608, 'src': 'embed', 'start': 2207.028, 'weight': 0, 'content': [{'end': 2210.371, 'text': "503, service unavailable, means maybe the server's overloaded or something like that.", 'start': 2207.028, 'duration': 3.343}, {'end': 2214.154, 'text': "And there's other codes there, but those are perhaps some of the most common ones.", 'start': 2210.431, 'duration': 3.723}, {'end': 2218.497, 'text': 'Has anyone, we can get away with this here, less so in New Haven.', 'start': 2215.255, 'duration': 3.242}, {'end': 2229.964, 'text': 'Has anyone ever visited safetyschool.org? http://safetyschool.org.', 'start': 2218.877, 'duration': 11.087}, {'end': 2231.605, 'text': 'Dare we do this? Enter.', 'start': 2229.984, 'duration': 1.621}, {'end': 2233.886, 'text': 'Oh, look at that.', 'start': 2232.906, 'duration': 0.98}, {'end': 2236.608, 'text': 'Where did we end up? OK, so.', 'start': 2233.946, 'duration': 2.662}], 'summary': '503 service unavailable is a common server error code.', 'duration': 29.58, 'max_score': 2207.028, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg2207028.jpg'}], 'start': 1745.343, 'title': 'Analyzing http headers and browsing data', 'summary': 'Explains the concept of http headers, their role in sending data when visiting a website, and the use of incognito mode for fresh browsing data. it also delves into analyzing the harvard website using developer tools, highlighting its 111 http requests totaling 20 megabytes, demonstrating http status codes, and revealing a humorous prank involving the rivalry between harvard and yale.', 'chapters': [{'end': 1809.823, 'start': 1745.343, 'title': 'Http headers and browsing data', 'summary': 'Explains the concept of http headers, their role in sending data when visiting a website, and the use of incognito mode for fresh browsing data.', 'duration': 64.48, 'highlights': ['HTTP headers are keys and values that browsers send every time a website is visited, including keys and values known as HTTP headers.', 'Browsers send HTTP headers like keys and values every time a website is visited.', 'Incognito mode is used to discard browsing history, ensuring that each request appears as a new one.']}, {'end': 2503.638, 'start': 1810.563, 'title': "Analyzing harvard's website", 'summary': 'Delves into analyzing the harvard website using developer tools, highlighting how it downloads over 111 http requests totaling 20 megabytes, demonstrates the use of http status codes, and reveals a humorous prank involving the rivalry between harvard and yale.', 'duration': 693.075, 'highlights': ['The Harvard website downloads over 111 HTTP requests, totaling 20 megabytes of information. The website is found to be downloading millions of bytes of information over 111 HTTP requests, demonstrating the heavy load on the website.', 'The demonstration of HTTP status codes such as 301 (Moved Permanently) and 404 (Not Found). The chapter explains the meaning of HTTP status codes, such as 301 indicating a permanent move and 404 indicating a resource not found, providing insight into how servers communicate with browsers.', 'A humorous prank involving the rivalry between Harvard and Yale is revealed through a video hosted on a domain name. The transcript uncovers a humorous prank involving the rivalry between Harvard and Yale, showcasing a video hosted on a domain name, adding a light-hearted touch to the technical content.']}], 'duration': 758.295, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg1745343.jpg', 'highlights': ['The Harvard website downloads over 111 HTTP requests, totaling 20 megabytes of information.', 'Browsers send HTTP headers like keys and values every time a website is visited.', 'Incognito mode is used to discard browsing history, ensuring that each request appears as a new one.', 'The demonstration of HTTP status codes such as 301 (Moved Permanently) and 404 (Not Found).', 'A humorous prank involving the rivalry between Harvard and Yale is revealed through a video hosted on a domain name.']}, {'end': 4003.504, 'segs': [{'end': 2842.824, 'src': 'heatmap', 'start': 2749.196, 'weight': 1, 'content': [{'end': 2753.46, 'text': 'port numbers to use and run our own web server on a web server.', 'start': 2749.196, 'duration': 4.264}, {'end': 2762.867, 'text': 'That is, we can control the environment entirely by just running our own web server via this command, http-server in my terminal window.', 'start': 2753.5, 'duration': 9.367}, {'end': 2765.71, 'text': 'This is a command that we pre-installed in VS Code here.', 'start': 2762.947, 'duration': 2.763}, {'end': 2767.291, 'text': "And you'll notice a pop-up just came up.", 'start': 2765.97, 'duration': 1.321}, {'end': 2770.013, 'text': 'Your application running on port 8080 is available.', 'start': 2767.331, 'duration': 2.682}, {'end': 2772.095, 'text': "That's a commonly used TCP port number.", 'start': 2770.033, 'duration': 2.062}, {'end': 2777.539, 'text': 'When 80 is already used and 443 is already used, you can run your own server on your own port, 8080 in this case.', 'start': 2772.135, 'duration': 5.404}, {'end': 2780.161, 'text': "I've opened that tab in advance.", 'start': 2778.72, 'duration': 1.441}, {'end': 2786.387, 'text': "And if I go into another browser tab here, here I see a so-called directory listing of the web server I'm running.", 'start': 2780.302, 'duration': 6.085}, {'end': 2788.469, 'text': "So I don't see any of my other files.", 'start': 2786.447, 'duration': 2.022}, {'end': 2791.472, 'text': "I don't see anything belonging to VS Code itself.", 'start': 2788.57, 'duration': 2.902}, {'end': 2795.836, 'text': "I only see the file that I've created in my current directory called hello.html.", 'start': 2791.552, 'duration': 4.284}, {'end': 2800.26, 'text': 'And so if I click on this file now, I should see Hello body.', 'start': 2796.157, 'duration': 4.103}, {'end': 2805.603, 'text': "I don't see the title, but that's because the title of a web page nowadays is typically embedded in the tab.", 'start': 2800.501, 'duration': 5.102}, {'end': 2808.165, 'text': "And if I'm full screen in my browser, there are no tabs.", 'start': 2805.903, 'duration': 2.262}, {'end': 2809.665, 'text': 'So let me minimize the window a bit.', 'start': 2808.205, 'duration': 1.46}, {'end': 2816.449, 'text': 'And now you can see just in this single browser window and my own URL here that hello body is in the top left-hand corner.', 'start': 2809.966, 'duration': 6.483}, {'end': 2818.77, 'text': "And if I zoom in, there's hello title.", 'start': 2816.489, 'duration': 2.281}, {'end': 2824.974, 'text': 'So what have I done here? I have gone ahead and created my own web page in HTML.', 'start': 2819.191, 'duration': 5.783}, {'end': 2828.836, 'text': 'in a file called hello.html.', 'start': 2825.834, 'duration': 3.002}, {'end': 2837.521, 'text': 'And then I have opened up a web server of my own, configured it to listen on TCP port 8080, which just says to the internet hey,', 'start': 2829.236, 'duration': 8.285}, {'end': 2841.743, 'text': 'listen for requests from web browsers, not on the standard port number 80 or 443..', 'start': 2837.521, 'duration': 4.222}, {'end': 2842.824, 'text': 'Listen on 8080.', 'start': 2841.743, 'duration': 1.081}], 'summary': 'Running a web server on port 8080, displaying hello.html file, and accessing it via a browser.', 'duration': 93.628, 'max_score': 2749.196, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg2749196.jpg'}, {'end': 3132.741, 'src': 'embed', 'start': 3101.193, 'weight': 0, 'content': [{'end': 3104.935, 'text': "It's an arbitrary tree that can have zero or any number of children.", 'start': 3101.193, 'duration': 3.742}, {'end': 3109.558, 'text': 'But if we have a special note here, that refers to the document, The root node, so to speak,', 'start': 3105.295, 'duration': 4.263}, {'end': 3112.621, 'text': "is HTML drawn with a rectangle here just for discussion's sake.", 'start': 3109.558, 'duration': 3.063}, {'end': 3115.444, 'text': 'It has two children, head and body, also rectangles.', 'start': 3113.042, 'duration': 2.402}, {'end': 3117.346, 'text': 'Head has a title child.', 'start': 3115.885, 'duration': 1.461}, {'end': 3121.79, 'text': "And then it and body have text nodes, which I've drawn with ovals instead.", 'start': 3117.666, 'duration': 4.124}, {'end': 3126.955, 'text': 'Which is only to say that when your browser Chrome, Safari whatever downloads a web page,', 'start': 3122.05, 'duration': 4.905}, {'end': 3132.741, 'text': 'opens up that envelope and sees the contents that have come back from the server, it essentially reads', 'start': 3126.955, 'duration': 5.786}], 'summary': 'The html tree consists of a root node with two children, head and body, and text nodes, illustrating the structure of a web page.', 'duration': 31.548, 'max_score': 3101.193, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg3101193.jpg'}, {'end': 3311.333, 'src': 'embed', 'start': 3286.384, 'weight': 2, 'content': [{'end': 3292.335, 'text': "And there's automated tools to check that, but we'll encourage you for problem sets and projects to use that particular manual tool.", 'start': 3286.384, 'duration': 5.951}, {'end': 3297.57, 'text': "All right, so let's go ahead and enhance this a little bit by introducing a whole bunch of tags,", 'start': 3293.069, 'duration': 4.501}, {'end': 3299.83, 'text': 'just to give you a sense of some of the building blocks here.', 'start': 3297.57, 'duration': 2.26}, {'end': 3305.411, 'text': "So I'm going to go ahead and create a new file called paragraphs.html.", 'start': 3300.13, 'duration': 5.281}, {'end': 3311.333, 'text': "And I'm just going to do a bunch of copy paste just to start things off so I'm not constantly typing all this darn stuff again and again.", 'start': 3305.811, 'duration': 5.522}], 'summary': 'Encouraging use of manual tool for problem sets and projects, introducing various tags for building blocks, creating paragraphs.html file for convenience.', 'duration': 24.949, 'max_score': 3286.384, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg3286384.jpg'}, {'end': 3500.108, 'src': 'embed', 'start': 3469, 'weight': 5, 'content': [{'end': 3473.144, 'text': 'So this is another tag, another three tags, h1, h2, h3.', 'start': 3469, 'duration': 4.144}, {'end': 3480.371, 'text': 'As you might have inferred by the file name I chose, this gives you headings, like in a book, different chapters or sections or subsections.', 'start': 3473.644, 'duration': 6.727}, {'end': 3484.034, 'text': "Or in an academic paper, you have different hierarchies to the text that you're writing.", 'start': 3480.411, 'duration': 3.623}, {'end': 3492.962, 'text': "So now that I've added an h1 tag, And the word 1, h2 tag, the word 2, h3 tag, and the word 3, let's go back to the browser, reload the page again.", 'start': 3484.455, 'duration': 8.507}, {'end': 3500.108, 'text': "And voila, once the page reloads, I'll do it with the manual button, reload the page.", 'start': 3492.982, 'duration': 7.126}], 'summary': 'Demonstrating the use of h1, h2, and h3 tags for different sections in a webpage.', 'duration': 31.108, 'max_score': 3469, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg3469000.jpg'}, {'end': 3954.948, 'src': 'embed', 'start': 3927.371, 'weight': 6, 'content': [{'end': 3936.416, 'text': "But if you've in advance uploaded a file to your own VS Code environment, like I did before class by dragging and dropping this photo of Harvard,", 'start': 3927.371, 'duration': 9.045}, {'end': 3939.417, 'text': 'you can just refer to it relatively so to speak.', 'start': 3936.416, 'duration': 3.001}, {'end': 3942.439, 'text': 'This would be the same thing as saying dot slash Harvard.jpg.', 'start': 3939.637, 'duration': 2.802}, {'end': 3945.921, 'text': 'go to the current directory, and get the file called harvard.jpg.', 'start': 3942.839, 'duration': 3.082}, {'end': 3947.803, 'text': "But that's unnecessary to type.", 'start': 3946.242, 'duration': 1.561}, {'end': 3954.948, 'text': "For accessibility purposes, though, for someone who's vision impaired, it's ideal if we also give this an alternative text,", 'start': 3948.223, 'duration': 6.725}], 'summary': 'In vs code, referencing files relatively saves time, enhancing accessibility with alternative text.', 'duration': 27.577, 'max_score': 3927.371, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg3927371.jpg'}], 'start': 2503.698, 'title': 'Html fundamentals and styling', 'summary': 'Covers the basics of creating a web page using html and css, explaining html fundamentals and syntax, html tags and building blocks, and creating and styling tables in html. it also emphasizes the importance of using correct tags and the hierarchical relationship between different elements.', 'chapters': [{'end': 2848.747, 'start': 2503.698, 'title': 'Introduction to html and css', 'summary': 'Introduces the basics of creating a web page using html and css, highlighting the distinction between programming languages and the structural and aesthetic elements, and also demonstrating the process of creating a web page and running a web server.', 'duration': 345.049, 'highlights': ['The chapter introduces the basics of creating a web page using HTML and CSS, emphasizing the distinction between programming languages like C, Python, and SQL, and the structural and aesthetic elements of HTML and CSS.', 'A demonstration of creating a web page in HTML using VS Code and incorporating the body and title elements, as well as specifying the language.', 'The process of running a web server on a custom TCP port (8080) to develop a website using a web-based tool, showcasing the ability to control the environment and view the web page in a browser.']}, {'end': 3286.364, 'start': 2849.147, 'title': 'Html fundamentals and syntax', 'summary': 'Explains the fundamental concepts of html such as tags, attributes, document structure and syntax, emphasizing the importance of indentation and the hierarchical relationship between different elements.', 'duration': 437.217, 'highlights': ['HTML is characterized by tags and attributes. The transcript highlights the key features of HTML, emphasizing the use of tags and attributes as the building blocks for structuring web pages.', 'Document type declaration specifies the HTML version. The document type declaration in HTML serves as a clue to the browser about the version of HTML being used, with the most recent version being succinct and informative.', "Importance of language attribute for translation and accessibility purposes. The language attribute in HTML, denoted by 'lang', provides a clue to the browser for automatic translation and accessibility purposes, with standardized two- and three-letter codes for human languages.", 'Hierarchy and structure of HTML elements. The transcript emphasizes the visual importance of hierarchy and nesting of HTML elements, defining the relationships between elements such as head, body, and the document root.', 'Significance of indentation for clarity and structure. The use of indentation in HTML is highlighted as a stylistic choice for clarity, aiding in the understanding of the structure and hierarchy of the code.']}, {'end': 3676.193, 'start': 3286.384, 'title': 'Html tags and building blocks', 'summary': 'Introduces the basics of html by demonstrating the use of tags such as p, h1, h2, h3, ul, and ol, and emphasizes the importance of using the correct tags for creating paragraphs, headings, and lists. the chapter also highlights the automatic numbering feature of the ol tag for ordered lists.', 'duration': 389.809, 'highlights': ['Introduction to HTML building blocks The chapter introduces the basics of HTML by demonstrating the use of tags such as p, h1, h2, h3, ul, and ol.', 'Importance of using correct tags Emphasizes the importance of using the correct tags, such as p for paragraphs, h1, h2, h3 for headings, ul for unordered lists, and ol for ordered lists.', 'Automatic numbering feature of ol tag Highlights the automatic numbering feature of the ol tag for ordered lists, making it useful for managing long lists of data.']}, {'end': 4003.504, 'start': 3676.513, 'title': 'Creating and styling tables in html', 'summary': 'Demonstrates how to create and structure tabular data using html, including the use of table, thead, tbody, tr, th, and td tags, and also discusses the inclusion of images in html, with the use of the img tag and alternative text for accessibility purposes.', 'duration': 326.991, 'highlights': ['The chapter discusses creating tables in HTML, using tags such as table, thead, tbody, tr, th, and td, to structure tabular data. This includes demonstrating the use of tags such as table, thead, tbody, tr, th, and td to organize and present tabular data.', 'The demonstration includes the use of the img tag for including images in HTML, and the importance of providing alternative text for accessibility purposes. The demonstration illustrates the usage of the img tag to include images in HTML, emphasizing the importance of providing alternative text for accessibility purposes.']}], 'duration': 1499.806, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg2503698.jpg', 'highlights': ['The chapter introduces the basics of creating a web page using HTML and CSS, emphasizing the distinction between programming languages like C, Python, and SQL, and the structural and aesthetic elements of HTML and CSS.', 'A demonstration of creating a web page in HTML using VS Code and incorporating the body and title elements, as well as specifying the language.', 'The process of running a web server on a custom TCP port (8080) to develop a website using a web-based tool, showcasing the ability to control the environment and view the web page in a browser.', 'HTML is characterized by tags and attributes. The transcript highlights the key features of HTML, emphasizing the use of tags and attributes as the building blocks for structuring web pages.', 'Document type declaration specifies the HTML version. The document type declaration in HTML serves as a clue to the browser about the version of HTML being used, with the most recent version being succinct and informative.', 'Introduction to HTML building blocks The chapter introduces the basics of HTML by demonstrating the use of tags such as p, h1, h2, h3, ul, and ol.', 'The chapter discusses creating tables in HTML, using tags such as table, thead, tbody, tr, th, and td, to structure tabular data. This includes demonstrating the use of tags such as table, thead, tbody, tr, th, and td to organize and present tabular data.']}, {'end': 4744.759, 'segs': [{'end': 4118.015, 'src': 'embed', 'start': 4088.723, 'weight': 1, 'content': [{'end': 4092.404, 'text': 'And that kind of makes sense for any attribute that really does what it says.', 'start': 4088.723, 'duration': 3.681}, {'end': 4095.525, 'text': "It doesn't make sense to say muted equals something.", 'start': 4092.624, 'duration': 2.901}, {'end': 4096.845, 'text': "It's either muted or not.", 'start': 4095.625, 'duration': 1.22}, {'end': 4098.145, 'text': 'The attribute is there or not.', 'start': 4096.925, 'duration': 1.22}, {'end': 4100.145, 'text': 'Similarly for these others as well.', 'start': 4098.606, 'duration': 1.539}, {'end': 4103.928, 'text': 'So let me go back to my other browser tab, reload the directory listing.', 'start': 4100.645, 'duration': 3.283}, {'end': 4110.111, 'text': 'There is both my mp4 and also video.html, which is the web page that embeds it.', 'start': 4104.408, 'duration': 5.703}, {'end': 4114.974, 'text': "And this is actually a video that was just on Harvard's website yesterday, and it was amazing.", 'start': 4110.471, 'duration': 4.503}, {'end': 4118.015, 'text': 'So we included it in this demo here.', 'start': 4115.094, 'duration': 2.921}], 'summary': "Attributes should be binary, like muted or not. also, included a video from harvard's website in the demo.", 'duration': 29.292, 'max_score': 4088.723, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg4088723.jpg'}, {'end': 4241.583, 'src': 'embed', 'start': 4214.837, 'weight': 0, 'content': [{'end': 4218.519, 'text': 'So we could change the width, change the height, get rid of that margin, and so forth.', 'start': 4214.837, 'duration': 3.682}, {'end': 4225.024, 'text': "But an iframe is a way of embedding someone else's web page in your web page, if they allow it,", 'start': 4218.559, 'duration': 6.465}, {'end': 4229.627, 'text': 'so as to create all the more of an interactive experience for them on, say, your site.', 'start': 4225.024, 'duration': 4.603}, {'end': 4232.771, 'text': 'All right, the web is, of course, known for things like links.', 'start': 4229.867, 'duration': 2.904}, {'end': 4236.016, 'text': "Let's go ahead and create a file called link.html.", 'start': 4232.851, 'duration': 3.165}, {'end': 4241.583, 'text': "And if we want to create a web page that actually links from itself somewhere else, let's go ahead and do this.", 'start': 4236.436, 'duration': 5.147}], 'summary': 'The transcript discusses customizing iframes and creating links in web pages.', 'duration': 26.746, 'max_score': 4214.837, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg4214837.jpg'}, {'end': 4493.272, 'src': 'embed', 'start': 4466.225, 'weight': 2, 'content': [{'end': 4472.248, 'text': 'There are special tags we can use to tell the browser to modify its display based on the hardware.', 'start': 4466.225, 'duration': 6.023}, {'end': 4475.049, 'text': 'So let me create a file called responsive.html.', 'start': 4472.568, 'duration': 2.481}, {'end': 4480.035, 'text': "I'm going to copy paste some in starting point here, call this title responsive.", 'start': 4476.59, 'duration': 3.445}, {'end': 4489.867, 'text': 'And let me go ahead and just grab some of that lorem ipsum text from before, just so that we have a sizable paragraph to play with here.', 'start': 4480.535, 'duration': 9.332}, {'end': 4493.272, 'text': 'And let me go ahead and grab this text here.', 'start': 4489.887, 'duration': 3.385}], 'summary': 'Using special tags for hardware-based display modification in responsive.html.', 'duration': 27.047, 'max_score': 4466.225, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg4466225.jpg'}], 'start': 4003.564, 'title': 'Video tag creation in html', 'summary': 'Discusses creating a video tag in html, specifying video source, and setting attributes like autoplay, loop, and mute. it also covers embedding videos using iframes, creating hyperlinks, and making web pages responsive, focusing on html tags, attributes, and values.', 'chapters': [{'end': 4110.111, 'start': 4003.564, 'title': 'Creating a video tag in html', 'summary': 'Discusses creating a video tag in html, including specifying the video source, setting attributes such as autoplay, loop, and mute, as well as understanding empty attributes, with an example of embedding a video file named halloween.mp4 and changing it to a file called video.html.', 'duration': 106.547, 'highlights': ['The chapter covers creating a video tag in HTML, setting the video source to halloween.mp4, and specifying its type as video/mp4, with attributes such as autoplay, loop, and mute, and setting the width of the video to 1,280 pixels wide, along with the concept of empty attributes.', 'The video tag allows attributes such as autoplay, loop, and mute, which can be used to control the behavior of the video player, and specifying the width of the video, for example, setting it to 1,280 pixels wide.', "The chapter explains the use of the video tag in HTML, including setting the source of the video to halloween.mp4, specifying its type as video/mp4, and using attributes like autoplay, loop, and mute to control the video player's behavior, as well as setting the width of the video element.", 'The chapter introduces the concept of empty attributes in HTML, such as autoplay, loop, and muted, which do not require values and are used for specific functionalities within the video tag, and provides an example of embedding a video file named halloween.mp4 and changing it to a file called video.html.']}, {'end': 4744.759, 'start': 4110.471, 'title': 'Web development basics', 'summary': 'Covers the basics of web development, including embedding videos using iframes, creating hyperlinks, and making web pages responsive to different devices, with a focus on html tags, attributes, and their values.', 'duration': 634.288, 'highlights': ["Creating embedded videos using iframes allows for interactive web experiences, with attributes like 'source' and 'allowfullscreen' providing customization options. Demonstrates the use of iframes to embed videos, with the ability to customize attributes like 'source' and 'allowfullscreen.'", "Hyperlinks are created using the 'a' tag with the 'href' attribute, enabling the linking of web pages with the specified URL and link text. Explains the process of creating hyperlinks using the 'a' tag and the 'href' attribute, allowing for linking to specified URLs with designated link text.", "The 'viewport' meta tag is used to make web pages responsive to different devices, specifying the initial scale and width to match the device's dimensions. Illustrates the use of the 'viewport' meta tag to optimize web page display for different devices by setting the initial scale and width to match the device's dimensions."]}], 'duration': 741.195, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg4003564.jpg', 'highlights': ['The chapter covers creating a video tag in HTML, setting the video source to halloween.mp4, and specifying its type as video/mp4, with attributes such as autoplay, loop, and mute, and setting the width of the video to 1,280 pixels wide, along with the concept of empty attributes.', "Creating embedded videos using iframes allows for interactive web experiences, with attributes like 'source' and 'allowfullscreen' providing customization options.", 'The video tag allows attributes such as autoplay, loop, and mute, which can be used to control the behavior of the video player, and specifying the width of the video, for example, setting it to 1,280 pixels wide.', "Hyperlinks are created using the 'a' tag with the 'href' attribute, enabling the linking of web pages with the specified URL and link text.", "The chapter explains the use of the video tag in HTML, including setting the source of the video to halloween.mp4, specifying its type as video/mp4, and using attributes like autoplay, loop, and mute to control the video player's behavior, as well as setting the width of the video element."]}, {'end': 6181.852, 'segs': [{'end': 4860.224, 'src': 'embed', 'start': 4832.782, 'weight': 3, 'content': [{'end': 4837.524, 'text': "So let's just delete it for now and leave it with the essence of that URL.", 'start': 4832.782, 'duration': 4.742}, {'end': 4838.744, 'text': 'And that still works.', 'start': 4837.804, 'duration': 0.94}, {'end': 4841.245, 'text': 'If I zoom out here, years ago you would get pictures of cats.', 'start': 4838.924, 'duration': 2.321}, {'end': 4843.306, 'text': 'Now you get videos of the movie.', 'start': 4841.305, 'duration': 2.001}, {'end': 4847.59, 'text': "And the top query there is cat's a bad movie.", 'start': 4845.527, 'duration': 2.063}, {'end': 4850.933, 'text': 'But we can also, of course, click on images.', 'start': 4848.671, 'duration': 2.262}, {'end': 4852.095, 'text': 'And there are the adorable cat.', 'start': 4850.993, 'duration': 1.102}, {'end': 4853.676, 'text': 'Oh, creepy cats.', 'start': 4852.175, 'duration': 1.501}, {'end': 4856.5, 'text': "All right, this didn't used to happen when we searched for cats.", 'start': 4853.736, 'duration': 2.764}, {'end': 4860.224, 'text': 'But anyhow, the point is that the URL changed.', 'start': 4856.56, 'duration': 3.664}], 'summary': 'The url content changed from cat images to movie videos.', 'duration': 27.442, 'max_score': 4832.782, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg4832782.jpg'}, {'end': 5162.615, 'src': 'heatmap', 'start': 4987.339, 'weight': 0.85, 'content': [{'end': 4994.102, 'text': "The form is going to use what method? Technically, it uses get by default, but I'll be explicit and say method equals quote unquote get.", 'start': 4987.339, 'duration': 6.763}, {'end': 5000.184, 'text': "Stupidly, it's lowercase in HTML, even though what's in the envelope is indeed uppercase by convention.", 'start': 4994.722, 'duration': 5.462}, {'end': 5008.396, 'text': "The action of this form specifically would ideally go to my own server, but we don't really have time today to implement Google itself.", 'start': 5001.144, 'duration': 7.252}, {'end': 5012.083, 'text': "So we're just going to send the user's request to google.com slash search.", 'start': 5008.456, 'duration': 3.627}, {'end': 5019.667, 'text': "So I'm creating a form, the action of which is to send the data to Google's slash search path using the get method.", 'start': 5013.226, 'duration': 6.441}, {'end': 5024.968, 'text': "It's going to send a input called q whenever I click this Submit button.", 'start': 5020.007, 'duration': 4.961}, {'end': 5028.009, 'text': 'Let me go back to the browser, reload the page.', 'start': 5025.288, 'duration': 2.721}, {'end': 5030.069, 'text': 'Nothing seems to have changed yet.', 'start': 5028.409, 'duration': 1.66}, {'end': 5037.511, 'text': "But if I search for, let me zoom out so we can see the URL bar, right now I'm in search.html.", 'start': 5030.269, 'duration': 7.242}, {'end': 5043.415, 'text': "If I zoom out and search for cats now and click Submit, I'm whisked away to google.com.", 'start': 5038.391, 'duration': 5.024}, {'end': 5050.58, 'text': 'But notice that the URL is parameterized with those key value pairs, that key value pair, and I get back a whole bunch of cat results.', 'start': 5043.475, 'duration': 7.105}, {'end': 5052.742, 'text': 'And I can very easily now make this a little prettier.', 'start': 5050.621, 'duration': 2.121}, {'end': 5057.286, 'text': "Right now, it's not ideal that the human has to move their cursor and click in the box.", 'start': 5053.122, 'duration': 4.164}, {'end': 5061.249, 'text': "And it's a little obnoxious that autocomplete is enabled if I don't want to search for cats anymore.", 'start': 5057.346, 'duration': 3.903}, {'end': 5065.092, 'text': "Well, according to HTML's documentation, I can say something like this.", 'start': 5061.669, 'duration': 3.423}, {'end': 5068.374, 'text': 'Autocomplete equals off to turn off autocomplete.', 'start': 5065.692, 'duration': 2.682}, {'end': 5072.418, 'text': 'Autofocus to automatically put the cursor inside of that text box.', 'start': 5068.755, 'duration': 3.663}, {'end': 5076.961, 'text': 'If I want some explanatory text, I can put placeholder text like, quote unquote, query.', 'start': 5072.758, 'duration': 4.203}, {'end': 5081.341, 'text': "And now if I go back to this page and reload, now it's a little more user friendly.", 'start': 5077.918, 'duration': 3.423}, {'end': 5083.664, 'text': 'You see query in kind of gray text.', 'start': 5081.642, 'duration': 2.022}, {'end': 5085.646, 'text': 'The cursor is already there and blinking.', 'start': 5083.924, 'duration': 1.722}, {'end': 5087.007, 'text': "I don't have to even move my cursor.", 'start': 5085.666, 'duration': 1.341}, {'end': 5088.429, 'text': 'I can search for dogs now.', 'start': 5087.287, 'duration': 1.142}, {'end': 5090.29, 'text': "And you didn't see any autocomplete at all.", 'start': 5088.489, 'duration': 1.801}, {'end': 5091.852, 'text': 'Hit Enter to submit.', 'start': 5090.31, 'duration': 1.542}, {'end': 5095.716, 'text': "And now I'm searching for, there we go, adorable dogs instead.", 'start': 5091.932, 'duration': 3.784}, {'end': 5101.32, 'text': "So what have I done? I've implemented the front end of google.com, just not the back end.", 'start': 5096.016, 'duration': 5.304}, {'end': 5105.803, 'text': "To implement the back end, we're obviously going to need a really big database, maybe something like SQL.", 'start': 5101.36, 'duration': 4.443}, {'end': 5110.347, 'text': "We're going to need some code that searches the database for dogs or cats or anything else.", 'start': 5106.043, 'duration': 4.304}, {'end': 5111.968, 'text': "We're going to need Python for something like that.", 'start': 5110.367, 'duration': 1.601}, {'end': 5115.33, 'text': "And in fact, that's the direction we're steering next week when we implement that back end.", 'start': 5112.248, 'duration': 3.082}, {'end': 5118.032, 'text': "But today, it's all about this front end.", 'start': 5115.49, 'duration': 2.542}, {'end': 5128.089, 'text': 'All right, any question then about forms, these URL parameters, before we now transition to making things look a little prettier with CSS.', 'start': 5118.753, 'duration': 9.336}, {'end': 5132.258, 'text': "And then we'll end by making things a little more functional with JavaScript.", 'start': 5129.031, 'duration': 3.227}, {'end': 5136.535, 'text': 'Anything at all? No? All right.', 'start': 5133.66, 'duration': 2.875}, {'end': 5144.201, 'text': "So let's start to answer a couple of the questions that came up by making these pages a little more aesthetically interesting.", 'start': 5136.735, 'duration': 7.466}, {'end': 5149.885, 'text': "Let's go ahead now and introduce to the mix one other language as follows.", 'start': 5144.381, 'duration': 5.504}, {'end': 5155.209, 'text': "Let me go ahead and create a file called home.html, as though I'm making a home page for the very first time.", 'start': 5149.965, 'duration': 5.244}, {'end': 5157.791, 'text': "And in this page, I'm going to give a title of home.", 'start': 5155.689, 'duration': 2.102}, {'end': 5159.913, 'text': "And I'm just going to have three things.", 'start': 5158.171, 'duration': 1.742}, {'end': 5162.615, 'text': "First, I'm going to have maybe a paragraph.", 'start': 5160.013, 'duration': 2.602}], 'summary': "Creating a form to send data to google's search using get method and making it user-friendly with html attributes. back end implementation planned for next week.", 'duration': 175.276, 'max_score': 4987.339, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg4987339.jpg'}, {'end': 5385.264, 'src': 'embed', 'start': 5361.184, 'weight': 1, 'content': [{'end': 5368.448, 'text': 'The semicolon just separates one key value pair from another, just like in the URL the ampersand did in the context of HTTP.', 'start': 5361.184, 'duration': 7.264}, {'end': 5371.31, 'text': 'The designers of CSS used semicolons instead.', 'start': 5368.808, 'duration': 2.502}, {'end': 5374.093, 'text': "Strictly speaking, this semicolon isn't necessary.", 'start': 5371.73, 'duration': 2.363}, {'end': 5378.157, 'text': "I tend to include it just for symmetry, but it doesn't matter because there's nothing after that.", 'start': 5374.413, 'duration': 3.744}, {'end': 5380.239, 'text': 'This is a bit of a weird example.', 'start': 5378.717, 'duration': 1.522}, {'end': 5385.264, 'text': 'This is the commingling of CSS inside of JavaScript.', 'start': 5380.639, 'duration': 4.625}], 'summary': 'Css designers used semicolons instead of ampersands; unnecessary for symmetry.', 'duration': 24.08, 'max_score': 5361.184, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg5361184.jpg'}, {'end': 5453.218, 'src': 'embed', 'start': 5429.367, 'weight': 5, 'content': [{'end': 5437.411, 'text': "I can actually magically say ampersand hash 169 semicolon using what's called an HTML entity.", 'start': 5429.367, 'duration': 8.044}, {'end': 5446.315, 'text': "Turns out there are numeric codes with this weird syntax that allow you to specify symbols that exist in Macs and PCs and phones but that don't exist on most keyboards.", 'start': 5437.791, 'duration': 8.524}, {'end': 5450.257, 'text': "If I reload the page now, now it's a proper copyright symbol.", 'start': 5446.735, 'duration': 3.522}, {'end': 5453.218, 'text': 'So minor aesthetic, but it introduces us to these HTML entities.', 'start': 5450.277, 'duration': 2.941}], 'summary': 'Html entities like © enable display of symbols not on keyboards.', 'duration': 23.851, 'max_score': 5429.367, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg5429367.jpg'}, {'end': 5589.186, 'src': 'embed', 'start': 5557.006, 'weight': 0, 'content': [{'end': 5561.728, 'text': "You might work with a designer, an artist, who's much better at all of these fine tunings aesthetically.", 'start': 5557.006, 'duration': 4.722}, {'end': 5564.408, 'text': "Wouldn't it be nice if you could work on the HTML,", 'start': 5562.048, 'duration': 2.36}, {'end': 5569.992, 'text': "they could work on the CSS And you don't have to somehow literally edit the same lines of code as each other?", 'start': 5564.408, 'duration': 5.584}, {'end': 5578.178, 'text': 'Well, just like we can move stuff into header files in C or packages in Python, we can do the same in CSS.', 'start': 5570.392, 'duration': 7.786}, {'end': 5579.859, 'text': "So I'm actually going to go ahead and do this.", 'start': 5578.478, 'duration': 1.381}, {'end': 5582.241, 'text': 'Let me get rid of all of these style attributes.', 'start': 5579.919, 'duration': 2.322}, {'end': 5589.186, 'text': 'And let me now start to practice a convention of not commingling CSS with my HTML.', 'start': 5582.781, 'duration': 6.405}], 'summary': 'Collaborate efficiently by separating html and css for clearer code maintenance and better teamwork.', 'duration': 32.18, 'max_score': 5557.006, 'thumbnail': 'https://coursnap.oss-ap-southeast-1.aliyuncs.com/video-capture/2VauFS071pg/pics/2VauFS071pg5557006.jpg'}], 'start': 4745.079, 'title': 'Front end development and web page styling', 'summary': 'Covers front-end development using html, css, and javascript, emphasizing the significance of url parameters and form implementation. it also demonstrates creating a basic web page with html and styling with css, including key concepts of semantic tags and style attributes.', 'chapters': [{'end': 5149.885, 'start': 4745.079, 'title': 'Front end development and url parameters', 'summary': 'Discusses the use of html, css, and javascript for front-end development, along with the implementation of url parameters and forms, highlighting the significance of url parameters and the implementation of form elements.', 'duration': 404.806, 'highlights': ["The significance of URL parameters and their implementation in web development is discussed, with examples from Google's search functionality and the use of key-value pairs in URLs. The chapter emphasizes the importance of URL parameters, illustrated by examples from Google's search functionality and key-value pairs in URLs.", "The implementation of form elements in HTML, including the use of methods such as 'get' and 'post', is explored, with a demonstration of creating a form and specifying its action and method attributes. The transcript delves into the implementation of form elements in HTML, including the demonstration of creating a form, specifying its action and method attributes, and discussing the use of 'get' and 'post' methods.", "The use of HTML attributes such as 'autocomplete', 'autofocus', and 'placeholder' to enhance user experience is demonstrated, showcasing how these attributes can improve the functionality and aesthetics of form elements. The chapter demonstrates the use of HTML attributes like 'autocomplete', 'autofocus', and 'placeholder' to enhance user experience and improve the functionality and aesthetics of form elements."]}, {'end': 5407.017, 'start': 5149.965, 'title': 'Creating a basic web page with html and styling with css', 'summary': 'Demonstrates creating a basic web page using html with three main sections, and then introduces styling using css with key concepts of semantic tags and style attributes, using key value pairs for styling properties.', 'duration': 257.052, 'highlights': ['The chapter demonstrates creating a basic web page using HTML with three main sections, which includes a header, main content, and footer.', 'Introduces the concept of semantic tags in HTML for better accessibility and search engine optimization, such as using