Hi   !

Would you please take a look at this article (scroll down some) :

http://techdows.com/2017/08/firefox-55-disable-hardware-acceleration.html

Any good  ?

That helped, thanks. It resolved my weird green screen on YouTube. This thing should be disabled by default.

You can try to set this pref to false on the about:config page instead of disabling hardware acceleration.

• media.windows-media-foundation.allow-d3d11-dxva

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

• http://kb.mozillazine.org/about:config