I don't know why no one replied. Maybe you're giving off a negative vibe? In February, you posted a question: "Sound and some video's don't work on facebook on my pc with firefox. Works fine on my phone with firefox . When I use a different browser on my pc it is fine." '''''Questions''''' What happens when you try to play a video on Facebook in Firefox on your PC. Is there an error message? Does it start and stop/stutter? Details would be helpful. How about other sites. Do videos play normally on YouTube? ---- Could you test in Firefox's Troubleshoot Mode? In that mode, Firefox temporarily deactivates extensions, hardware acceleration, any userChrome.css/userContent.css files, and some other advanced features to help you assess whether these are causing the problem. ''If Firefox is running:'' You can restart Firefox in Troubleshoot Mode using either: * "3-bar" menu button > Help > Troubleshoot Mode... * (menu bar) Help menu > Troubleshoot Mode... and OK the restart. A small dialog should appear. Click the Open button. ''If Firefox is not running:'' Hold down the Shift key when starting Firefox. (On Mac, hold down the option/alt key instead of the Shift key.) A small dialog should appear. Click the Open button. ''Note: Don't use the Refresh without first reviewing this article to understand what will be deleted:'' [[Refresh Firefox - reset add-ons and settings]]. Any improvement? Ref. [[Diagnose Firefox issues using Troubleshoot Mode]] ---- In case you need the URL to this thread: https://support.mozilla.org/questions/1498541