Can't restore colors
Firefox 41.0.1 If you, as I do, set the colors to text white and background medium grey, you're dead in the water trying to restore them because the tools/options/content page is white.
Opaite Mbohovái (2)
Can you reset the browser.display.* prefs on the about:config page?
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.
If that isn't possible then you can edit the prefs.js file in the Firefox profile folder and remove all browser.display.* prefs.
- user_pref("browser.display.*", <data>);
You can use this button to go to the current Firefox profile folder:
- Help > Troubleshooting Information > Profile Directory: Show Folder (Linux: Open Directory; Mac: Show in Finder)
- http://kb.mozillazine.org/Profile_folder_-_Firefox
You can look at this extension to adjust the font size in the user interface.
- Theme Font & Size Changer: https://addons.mozilla.org/firefox/addon/theme-font-size-changer/
You can set a global Zoom that affects both the user interface and web pages (this modifies the layout.css.devPixelsPerPx pref). You can do this via the Options/Preferences of the extension (about:addons or the Tools menu).
Moambuepyre cor-el rupive
If you have trouble doing the above,
Start Firefox in Safe Mode {web Link} by holding down the <Shift>
(Mac Options) key, and then starting Firefox.