What Does HTML5 Include?

By 2007, all the excitement was in the WHATWG camp. After some painful reflection, the W3C decided to disband the group that was working on XHTML 2 and work on formalizing the HTML5 standard instead. At this point, the original HTML5 was broken into more manageable pieces, and many of the features that had originally been called HTML5 became separate standards.

There’s no such thing as a browser that “supports” HTML5. Instead, every browser supports a gradually expanding subset of HTML5 related features. This approach is both good and bad. It’s good because the browsers can quickly implement mature parts of the HTML5 standard while other features continue to evolve. It’s bad because it forces web page writers to worry about checking whether a browser supports each feature they want to use. (You’ll learn about the painful and not-so-painful techniques to do so in this book.)
Here are the major feature categories that fall under the umbrella of HTML5:

The Story of HTML5

As you know, HTML is the language you use to write web pages. The basic idea of HTML—that you use elements to structure your content—hasn’t changed since the Web’s earliest days. In fact, even the oldest web pages still work perfectly well in the most modern web browsers (including several browsers that didn’t exist at the time, like Firefox and Chrome).
Being old and successful also carries some sizable risks—namely, everyone wants to replace you. In 1998, the W3C stopped working on HTML and attempted to improve it with an XML-powered successor called XHTML 1.0.