Does that happen all the time or only on specific pages? On some page that have a background image with a white background the selection color may not be very noticeable, only if you look good you can see a slight change in the color of the selected text and no background color change. If that didn't apply then start Firefox in [[Safe Mode]] to check if one of the add-ons is causing the problem (switch to the DEFAULT theme: Tools > Add-ons > Themes). * Don't make any changes on the Safe mode start window. See: * [[Troubleshooting extensions and themes]]