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.