Here’s more than you want to know about why there’s no video codec standard in HTML 5. Ryan Paul in Ars:
The HTML 5 working group is split between supporters of Ogg Theora and H.264. Their inability to find a compromise that is acceptable to all stakeholders has compelled HTML 5 spec editor Ian Hickson to “admit defeat” and give up on the effort to define specific codecs and media formats in the standard itself. This is problematic because the lack of uniform codec availability will make it impossible for content creators to publish their videos in a single format that will be viewable through the HTML 5 video element in all browsers.
Browser vendors are selfish, childish, irresponsible bullies who won’t play unless they get their own way.