HTML5 has gained a lot of supporters in the last few years, including tech giants Microsoft, Google, and Apple. On the other hand, the World Wide Web Consortium (W3C), which oversees HTML5, warns the specification isn't yet ready for website deployment.
W3C wasn't even in the group that developed HTML5. Another grouped was formed, WHATWG, founded by individuals from Apple, the Mozilla Foundation and Opera Software to develop the HTML5 specification since W3C was stalling on the development of new web technologies and they were only working on the XHTML 2.0, which sucked (including v1). Later XHTML 2.0 development was dropped and W3C got involved in the development of HTML5.
And there's also the fact that HTML5 is one thing, CSS3 is another, Canvas another, etc. So really what do you think HTML5 is?