If you have been tweaking your firefox browser with different add-ons, hacks etc but now you want to restore the original settings in firefox without reinstalling it, here is a simple procedure.

–Open Firefox in Safe Mode, from your programs menu or by typing “firefox -safe-mode” in Start->Run.

–At this point a dialog box should appear asking you to perform different actions before opening the browser. These options include: Disable add-ons, Reset Toolbar and Controls, Reset bookmarks to Firefox defaults, Reset all user preferences to Firefox defaults, Restore default search engines.

–In order to restore default settings , tick all option but the first one.

–Now click the Make Changes and Restart button.