Firefox video issues (html5)

Stacey started a channel on youtube with an introductory video that was in mp4 format. My laptop would play it, but my desktop would not. No google searches yielded a solution, but one hinted that firefox html5 support is not yet complete, and in fact html5 isn't really there yet. Poking around in the source of the error page made it clear that the video was coming in through html5. By clicking on the error message from youtube, I found a link at the bottom that offered to remove me from the "html5" trial. I vaguely remember joining this effort over a year ago when I was playing with html5 on my own web site. Clicking on this solved the problem. The reason I did not have the problem on the laptop is because I was not logged in, so youtube did not pick up the html5 trial flag.