Best Video Format ?

Just curious, what is the best video format for putting our own video clips on our WP install (not YouTube)?

Here is an example of one that we created in MP4. It plays fine in Chrome and Safari, but not in Firefox4. I’m just wondering if it’s us, or the browser?

http://www.leftcoastlogic.com/blog/sc3/

code is

<p style="text-align: center;"><embed width="720" height="495" src="http://www.leftcoastlogic.com/blog/wp-content/uploads/2011/05/ex15.mp4"></embed></p>