hello iglika_h,

follow the steps:

1) Clear all cookies, site data and cache

• Click the menu button. and select Options.
• Select the Privacy & Security panel and go to the Cookies and Site Data section.
• Click the Clear Data… button. The Clear Data dialog will appear. ...
• Click Clear.

2) Reset the Zoom of the web pages:

• ctrl+0.
• manual control zoom in zoom out :
• click 3 horizontal lines top right on browser screen.
• click zoom + or -;

3) Reset the minimum font size

Type the address about:preferences in the address bar and hit Enter.

Scroll down to Fonts and Colors and click on Advanced…

Change the value of Minimum font size to None.

4) Reset the page style of the web page

Press ALT while keeping the Firefox browser open. This will display the traditional Firefox menu on the top of the window.

Select View > Page Style > Basic Page Style

Restart the Firefox browser and check if the issue is resolved or not.

Thank you!

Hello, I did follow steps as you described. I did it 3 times. Flickering still exist in same way as it was before. Is there something else I could try?

You can try to disable hardware acceleration in Firefox.

• Options/Preferences -> General: Performance
  remove checkmark: [ ] "Use recommended performance settings"
  remove checkmark: [ ] "Use hardware acceleration when available"
• https://support.mozilla.org/en-US/kb/performance-settings

Close and restart Firefox after modifying the setting for changes to take effect.

• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems
• https://support.mozilla.org/en-US/kb/upgrade-graphics-drivers-use-hardware-acceleration

Start Firefox in Safe Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration is causing the problem.

• switch to the DEFAULT theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

suggested steps did not solve flickering.