Except for the videos on YouTube that don't support HTML5 yet. From here[1]:
| Additional Restrictions (we are working on these!)
|
| - Some videos with ads are not yet supported (they
| will play in the Flash player)
|
| - On Firefox and Opera, only videos with WebM
| transcodes will play in HTML5
|
| - If you've opted in to other testtube experiments,
| you may not get the HTML5 player (Feather is
| supported, though)
The YouTube HTML 5 player is basically done now, it works just as well as the flash one. I wish they would stop "experimenting" and roll this out across the site. They seem to have no timeframe for releasing it.