I don't think this is what yuhong was referring to, but there's a lot wrong with HTML5. Googling "w3c whatwg", as one commenter suggested, won't give you any real insight into the mess, but it will hint at it.
TL;DR The above document is irrelevant and should be ignored. Popular browsers' implementations define the HTML5 that most devs will want to target, and those browser vendors are members of the competing WHATWG body. They will largely ignore the W3C copy.
TL;DR The above document is irrelevant and should be ignored. Popular browsers' implementations define the HTML5 that most devs will want to target, and those browser vendors are members of the competing WHATWG body. They will largely ignore the W3C copy.