Hello and welcome to our lecture on HTML, the Hypertext Markup Language. So I'm going to place this in the context of our request-response cycle, and sort of here's us in the request-response cycle in our browser and what we're seeing. We make a click, it goes across the network to the web server, runs some code, maybe talks to a database, formats up some new stuff, and we get the response. Then HTML comes out, and then that's parsed to make the DOM and what we see is the Document Object Model. And we're going to ignore most of that in this lecture. We are really only going to talk about this part here and that is what this response is. It's HTML and it is parsed and it's read through and it's used to construct the Document Object Model, which then shows what we see. And so HTML is just a technique of using some special characters, less than and greater than, to add tags to indicate what we want to see, like the paragraph tag. The paragraph tag, that's a paragraph tag, strong tag makes things bold, emphasize tag, and a paragraph tag. And so we have these tags and we just mark up, we're communicating meaning. If you're old enough to remember, old word processors used to have ways to look at the actual codes that were being stored in the word processor file. So the web is, the HTML and Hypertext Transport Protocol and all that stuff is a relatively recent invention and we're doing so many cool things with it. It's continuously evolving and it really we're less than 20 years old, but we're doing so much with it, it's continuously evolving. So HTML and CSS are really kind of at the edge. Looking back in the early days, if we take a look at what HTML was really intended to do, it worked on a NeXT computer in the early 1990s. And so this is the NeXT browser which came from CERN. And it had everything in a new window, images were not shown inline. And then there was the NCSA Mosaic browser, which was the first browser that was universally available on Unix, Windows, and Macintosh. And you see things like a gray background and blue links and highlighted links that you visited in purple. And so in the early days, it was nothing like what we see today. In the early days, we were just amazed and happy that we could see a link and you'd click the link and something would happen. But today, money has is be made based on making stuff super beautiful and the number of pixels and how things line up and how things are shoved over and how navigation looks. And so today we need to create beautiful web pages, whereas in the old days, we were just amazed to have web pages that worked in the first place. And of course, computers have gotten much faster, are capable of handling video and images. Back in the old days, images were costly, both for network bandwidth and for the time it took your computer to display them, and so that just affected how we did it. And it's kind of fun to use the Wayback Machine, otherwise known as the Internet Archive, to go back and look at some of these older web pages and realize that it's still amazing that a lot of them pretty much work. And in the good old days, HTML was kind of a wild west. The browsers did not want to show broken HTML as broken HTML and so they compensated for it. And so in the old days we had things like tags that could be uppercase, we would have a paragraph tag that didn't finish, we would have li tags that didn't finish, we would have attributes that didn't even have double quotes in them. So there was all kinds of stuff and literally you could take this bad page and you could put it into a web browser and it will still display. So HTML, while it technically is a very precise language and you can make syntax errors, browsers are extremely flexible in terms of parsing it. Now, you're not going to get predictable results, the browsers can go into what's called quirks mode. And so in order to create the standards environment that we have today, Tim Berners-Lee, one of the original founders of the World Wide Web, helped found an organization called the World Wide Web Consortium or the W3C and it really decided that instead of just letting people write a browser and having HTML be defined by the browser, instead they would write a spec for what HTML was and then multiple vendors could produce the browsers. And it took a while for this to become successful but there was a need for every vendor to build a web browser and so they worked with the World Wide Web Consortium. And like the mid and late 90s, '95, well '94 through '98, '99, the World Wide Web Consortium created a lot of wonderful standards around the World Wide Web. Now, once we started having rules, then we tend to want to follow those rules. And so tags need to be lowercase, attributes like this image source equals have to have double quotes around them, you have to have open tags and close tags. And so there's a set of rules and now we are much more precise about our HTML. We try to write it as precise as we can so that we get the best performance and the best sort of rendering out of the browsers that we can possibly get. Because if you don't write precise HTML, then the browsers are going to make decisions as to how to render things, whereas if you write precise HTML, then you really are in control of how the browser lays things out. So, up next we're going to talk about HTML itself, look at some HTML documents, and take a look at the syntax of HTML. [MUSIC]
