Hello,

Try Firefox Safe Mode to see if the problem goes away. Safe Mode is a troubleshooting mode, which disables most add-ons.

(If you're not using it, switch to the Default theme.)

• On Windows you can open Firefox 4.0+ in Safe Mode by holding the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac you can open Firefox 4.0+ in Safe Mode by holding the option key while starting Firefox.
• On Linux you can open Firefox 4.0+ in Safe Mode by quitting Firefox and then going to your Terminal and running: firefox -safe-mode (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)
• Or open the Help menu and click on the Restart with Add-ons Disabled... menu item while Firefox is running.

Once you get the pop-up, just select "'Start in Safe Mode"

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one. Please follow the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article for that.

To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help other users who have the same problem.

Thank you.

Hello Shaya, Does this happens in Firefox only?? Have you tried ohter browser to play the video on youtube (like Chrome, opera ).

please detail your query a little bit more so we can help you more efffectively.

Chrome is working youtube only firefox it does play youtube thankx

Check your plugins are up-to-date!

   http://www.mozilla.org/en-US/plugincheck/ 

Type about:addons in URL and Goto Plugins

   Check all the plugins are "Always Active" 

Somewhere on the page right click, go to view page info > permissions and make sure that adobe flash content is allowed to play on that domain.

Also Try these:

Clear the cache and cookies only from websites that cause problems.

"Clear the Cache":

   Firefox/Tools > Options > Advanced > Network > Cached Web Content: "Clear Now" 

"Remove Cookies" from sites causing problems:

   Firefox/Tools > Options > Privacy > Cookies: "Show Cookies" 

Please Reply to us if it was helpful or not.

Thank you.

Thank you

Its our Pleasure to help you. Enjoy your Videos with Firefox and feel free for any more queires.

Thank You