I have not seen that before. Sometimes Firefox makes errors painting the screen with certain graphics card drivers. A common test is to disable hardware acceleration to see whether that makes any difference. It is now under: Firefox's performance settings.

Otherwise... ??

Nothing happens. Here is the addon to check: https://addons.mozilla.org/en-US/firefox/addon/youtubehd/ for others if is work. On 56.0.2 (64-bit) its works fine. In 57.0 (64-bit) not.

uninstall Firefox. Then Delete the Mozilla Firefox Folders in C:\Program Files and C:\Program Files(x86) Then restart system. Then run Windows Disk Cleanup. Then run it again and click the button that says Cleanup System Files. Note: your Firefox Profile is saved. But you should make a back up before you do : https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles

Reinstall with Current Release Firefox 57.0 with a Full Version Installer https://www.mozilla.org/firefox/all/

Please let us know if this solved your issue or if need further assistance.

I uninstall the firefox, cleanup and delete all files. Update video card. Install x32. I install on Windows 10 on Virtual Machine is the same.

Nothing works.

Is version 58.0 and is still there :(

You probably prefer smooth scrolling, but does the problem stop if you disable it? You can find that on the Options/Preferences page:

You can check that here:

• Windows: "3-bar" menu button (or Tools menu) > Options
• Mac: "3-bar" menu button (or Firefox menu) > Preferences
• Linux: "3-bar" menu button (or Edit menu) > Preferences
• Any system: type or paste about:preferences into the address bar and press Enter/Return to load it

In the search box at the top of the page, type smo and Firefox should filter to the "Browsing" section where you can uncheck (clear) the checkbox for "Use smooth scrolling".

Does that make any difference?

No changes.