Hello,

Try Firefox Safe Mode to see if the problem goes away. Firefox Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes).

If Firefox is open, you can restart in Firefox Safe Mode from the Help menu:

• Click the menu button , click Help and select Restart with Add-ons Disabled.

If Firefox is not running, you can start Firefox in Safe Mode as follows:

• On Windows: Hold the Shift key when you open the Firefox desktop or Start menu shortcut.
• On Mac: Hold the option key while starting Firefox.
• On Linux: Quit Firefox, go to your Terminal and run firefox -safe-mode
  (you may need to specify the Firefox installation path e.g. /usr/lib/firefox)

When the Firefox Safe Mode window appears, select "Start in Safe Mode".

If the issue is not present in Firefox Safe Mode, your problem is probably caused by an extension, theme, or hardware acceleration. Please follow the steps in the Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems article to find the cause.

To exit Firefox Safe Mode, just close Firefox and wait a few seconds before opening Firefox for normal use again.

When you figure out what's causing your issues, please let us know. It might help others with the same problem.

Diego Victor said

Try Firefox Safe Mode

Thanks, but the same in safe mode!

Open about:config and try this setting:

• gfx.use_text_smoothing_setting; - set to true

finitarry said

Open about:config and try this setting:

• gfx.use_text_smoothing_setting; - set to true

Thanks, not helped either.

I switched OS and on the same PC the font is fine, so I think there is a problem with the amd drivers that are old and not updated in Vista

Are you using Cleartype with the operating system? That helps everywhere.

You can try to disable OMTC and leave hardware acceleration in Firefox enabled.

• about:config page: layers.offmainthreadcomposition.enabled = false

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

See also:

• https://support.mozilla.org/kb/upgrade-graphics-drivers-use-hardware-acceleration

finitarry said

Are you using Cleartype with the operating system? That helps everywhere.

I think yes

cor-el said

You can try to disable OMTC and leave hardware acceleration in Firefox enabled.

• about:config page: layers.offmainthreadcomposition.enabled = false

I will try it next time, for now I will mark it as the correct answer.