Used Easy HYML5 Video to get the html for a video that has full screen option but when previewed in Firefox, the full screen option is not available. It works fine in Safari so it is a Firefox issue.
Mac OS 10.6.8 Snow Leopard Firefox 8.0.1 Easy HTML5 Video app http://easyhtml5video.com/ This app writes the HTML for embedding video in a web page WITH the option of viewing full screen. When I preview the page with Firefox, the full screen option is not available. When I preview it with Safari, it is and works as it was meant to work. I have no problem watching YouTube video full screen (as suggested in one of you FAQ answers)
Opaite Mbohovái (1)
Probably a minor web page coding issue.
You could try posting the code you're using over at the Web Development / Standards Evangelism forum at MozillaZine. The helpers over there are more knowledgeable about web page development issues with Firefox.
http://forums.mozillazine.org/viewforum.php?f=25
You'll need to register and login to be able to post in that forum.
Support for that Easy HTML5 program is listed at the bottom of thus page.
http://easyhtml5video.com/index.html#help