Problem: You can’t play any youtube videos on firefox browser, yesterday you had no problems viewing any youtube videos but today all the videos on youtube website appear as a black screen, you don’t have any problems with intenret explorer or google chrome.
1) Solution 1: Disable Shockwave Flash plugin in firefox and restart firefox.
2) Solution 2: Delete the history and all cockies on firefox and restart it.
3) Solution 3: If you have Adblock Disable it and restart firefox.
4) Solution 4: Disabled all the extensions and the add-on in firefox and restart it.