iPad 2: watching YouTube movies full screen via HDMI

I'm trying to watch movies via YouTube, or Vimeo, etc full screen from my iPad to my HDMI tv. I have my iPad connected via HDMI to my tv.

I can watch full screen movies from my Netflix app, but browsers (Safari, FireFox) have this problem:

I'll find a movie on YouTube. When I click on the icon to make the video full screen to my HDMI tv, I only get sound. On the iPad a progress bar (with play /pause) appears at the top of the screen. The video will only play within the browser window. It won't play in full screen.

Hmmm.

Any clues.