http://support.mozilla.com/en-US/kb/Youtube+HTML5+does+not+work+in+Firefox

TXGuy, that page you've linked to is out of date, it only talks about Theora video, not webm. I'm seeing the same problem as AnonymousUser if I have my privacy preference set to not accept cookies from sites. I've made an exception for youtube (Tools > Page Info > Permissions > Set Cookies > Allow) so I could opt in to their html5 beta, but it makes no difference to the problem. If I want to watch a webm youtube video I have to set "Accept cookies from sites" as a global preference

See also https://developer.mozilla.org/En/Media_formats_supported_by_the_audio_and_video_elements

Make sure that the server sends the video files with the correct MIME (content) type, otherwise Firefox won't play them.

I had the same problem too. I found a tutorial on Lynda.com that was very helpful. I needed to configure my server to deliver html5 formats. This requires a .htaccess file. You can put it in any directory and it will not effect directories above, just within that folder or below. It is simple a txt file that has code like this:

AddType video/mp4  mp4 m4v
AddType audio/mp4  m4a
AddType video/ogg  ogv
AddType audio/ogg  ogg oga
AddType video/webm webm

Make sure that when it is uploaded, it is renamed to not include the .txt. The file name should be .htaccess Let me know if you have questions with this. I have been pulling my hair out over this for weeks and am so happy to finally have it playing on Firefox. Hope this helps....

Thank you so much, avanluv77!

I just updated to Firefox 8.0 and the .webm/.mp4 versions of my HTML5 videofile wouldn't show. I included your code in my .htaccess and now everything is fine!!

I have tried updating the .htaccess file but the video does not play in html5 video tag. However when I copy the location of the file, I could play the video directly.

Donno whats the problem...

my code:

• source src="videos/01.mp4" type='video/mp4' />
• source src="videos/01.webm" type='video/webm' />

replace * with <

Did you check with which content type the server sends the file?

Live Http Headers:

• https://addons.mozilla.org/firefox/addon/live-http-headers/