Try to clear the cache and remove the cookies from sites that cause problems. * Extras > Einstellungen > Erweitert > Netzwerk > Zwischengespeicherte Webinhalte: Jetzt leeren * Extras > Einstellungen > Datenschutz > Cookies > Cookies anzeigen Start Firefox in <u>[[Safe Mode|Safe Mode]]</u> to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance). *Do not click the Reset button on the Safe mode start window or otherwise make changes. *https://support.mozilla.org/kb/Safe+Mode *https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes