I\'m a desktop application developer, and I plan learning html5, but as it\'s not released, there are (almost) no published books and not too much infomation for beginners on th
HTML5 is basically the same as HTML4 but with some nice additional little features. Pretty much everything you will learn from HTML4 will work seamlessly in a HTML5 environment.
I would start with learning things in this order: HTML4, then CSS2, then jQuery.
After that, start learning about HTML5 and CSS3 when more information comes out about them. But main issue about learning these languages falls down to your basic understanding. Once you have that in place, the newer technologies just make these basic things a bit easier.
Effectively, they will always be written and constructed in more or less the same way - but in time with newer versions, things will become increasingly easier to achieve.