Hi pternagy, Sorry you are having problems. For future reference. Those of us that mess directly with about:config soon learn how to recover from mistakes and what it is sensible to backup. Occasionally backing up your entire profile for instance can be useful and would have probably given you a quick solution of copying over the file from that backup. *[[Back up and restore information in Firefox profiles]] Ok on to the subject of trying to get Firefox back as it was: Find your profile and the file ''prefs.js'' and rename that. (The renamed file is a potentially useful backup.) Firefox is then forced to regenerate the file and will reset your preferences to the default. You can then re open and use Firefox. Next try to get it back to normal. Trying to manually edit the file ''prefs.js'' is normally a bad idea. However if it is a single pref change it may be possible to directly edit the prefs.js file (whilst Firefox is closed) to get everything back to how it was before . You have the renamed file to work with. Probably best to test all this out in a new additional profile then you only break additional test profiles not working profiles essential to Firefox. These articles should help you: * http://kb.mozillazine.org/Prefs.js_file * [[Reset Firefox preferences to troubleshoot and fix problems#w_solution-2-delete-firefox-preference-files]]_solution-2-delete-firefox-preference-files *[[Profiles - Where Firefox stores your bookmarks, passwords and other user data#w_finding-your-profile-without-opening-firefox]]#w_finding-your-profile-without-opening-firefox * http://kb.mozillazine.org/Using_multiple_profiles_-_Firefox Please post back with how you get on and whether you need any extra help. Good Luck.

Thanks. That helped a lot. As I suspected, it was the change in Java setting.s

You’re welcome. Thanks for posting back. Glad it is working again.