HTML5, the emerging successor to HTML and XHTML, has in one form or another been an under-development web specification since 2004. But it wasn’t until 2009 that HTML5 began to break through as something that would really happen. Two prominent examples from last year that HTML5 would be part of our web future: The news last May from Google I/O 2009 that Google is betting big time on HTML5; and Jeffrey Zeldman’s influential pronouncement that HTML5 deserves your love. (Loyalty oath, optional; specification details to be worked out.) At this year’s Google I/O 2010 the Google crush on HTML5 was apparently on full display.

Want more proof? Last year you couldn’t drop a dime to find a book about HTML5. Now at Amazon you will find 10+ books about HTML5, most of which are still in publication pre-order status. And coming next month is the one HTML5 title I know I must have: HTML for Web Designers by Jeremy Keith, only available directly from the publisher A Book Apart. (Jeremy Keith is the author of DOM Scripting: Web Design with JavaScript and the Document Object Model, which I have read and do recommend. The guy is a really great, first-tier tech writer.)

Which leads me to what actually prompted me to write this post in the first place: Among the newest of podcasts I now consider a must-listen is Zeldman’s The Big Web Show. The second show in this weekly podcast was the hour-long HTML5 with Jeremy Keith. Call me a nerd, call me a geek, call me irresponsible, but it is the only podcast I have ever listened to twice. It was that good.

It’s a start: Seven HTML related working drafts published, posted today at 456 Berea Street and referencing among others a first version of HTML: The Markup Language (“Basically ‘HTML 5′ for web developers,’ i.e., “HTML syntax, elements, and attributes without the implementation details”); and the newest version of HTML5 differences from HTML4 (“How and why HTML 5 is different from HTML 4, in particular regarding new, changed, and absent elements and attributes.”)