MichaelBluejay - 7:07 am on Nov 30, 2011 (gmt 0)
It's not HTML5's fault, it's Firefox's fault for refusing to support mp4. Since Firefox doesn't play mp4 files, you have to feed Firefox a file in the relatively rare "ogg" format.
BTW, I don't buy Firefox's argument that they're boycotting mp4 because it's a proprietary format and they want to support only free formats so the world can be simple and free. The reality is that their refusal to support mp4 makes the world *hard* and *complicated* because it's a pain for webmasters to get video onto their sites that will work in all browsers. Some gift they've given to the web community, there.
You mentioned three formats -- what's the third you were thinking of, Flash? What besides Firefox doesn't play mp4?