You may need the flash player required to play those types of files or you may need to update your plugins.

Please check if all your plugins are up-to-date. To do this, go to the Mozilla Plugin Check site.

Once you're there, the site will check if all your plugins have the latest versions. If you see plugins in the list that have a yellow Update button or a red Update now button, please update these immediately.

To do so, please click each red or yellow button. Then you should see a site that allows you to download the latest version. Double-click the downloaded file to start the installation and follow the steps mentioned in the installation procedure.

If this happens on YouTube then try to opt-out of HTML5 (Firefox doesn't support MP4 via a video tag).

• http://www.youtube.com/html5/

Thanks for the info. I checked my plugins as was suggested, and my Shockwave player was not up-to-date. Updating this plug-in fixed the problem for me.

Many thanks,

George

Problem solved! I downloaded and installed Firefox 24.0 Beta. Apparently Mozilla programming team made all the right changes in the new release. Now all videos starting working on Yahoo and BBC and other sites

Link: http://www.mozilla.org/en-US/firefox/channel/#beta