You are probably here because your Youtube decides to show you a green screen rather than the actual video. You may have realized that you can hear the audio perfectly. This annoying glitch is very common, it is very likely to happen after upgrading to Windows 8.
So here is a simply tutorial on how to fix this glitch.
Whenever you launch a video such as the one shown below (this is one that I made!) you receive this green colour that covers your video. All you have to do is right click on the green area and click on "Settings".
You will get this small popup, all you have to do is untick the "Enable hardware acceleration" option.
Now refresh the page and your video is working! You only need to do this once and it will work for all your videos!
So I hope I helped you fix your Youtube. If you're still having problems tell me in the comments and I will be quick to help. And please consider sharing this useful tip with your friends using any of the share buttons below.