HyperText Markup Language 4 as we know it has not changed since 1999, but as we know from being a part of the internet culture and development of it, that things have evolved in the past 8 years. CSS, JavaScript, and XML have really changed what we can accomplish and create for the world to read, use, or play with.

Back in 2004 the next phase of HTML was being pioneered by the WHATWG (Web Hypertext Application Technology Working Group). Oh yeah, them you say. In 2007 the W3C passed HTML5 on to the HTML working group and made it their primary focus. For the past few month quite a few documents have been created outlining the new and forth coming HTML5.

When will HMTL5 be ready for use or be finished? Your guess is as good as mine and it may never reach a completed or finished phase, but some features of HTML5 can already be used. One such tag is <canvas>. Here's a Mozilla Tutorial for the <canvas> tag. It's an element that can work together with JavaScript for rendering images and animations in a specified canvas size. See the example link above.

Other new elements expected for HTML5 are - section, video, progress, nav, meter, time, aside. You can get a run down of what these elements are and there purpose at the W3C. Reference it here.

Read more here:
wiki HTML5
New Elements