How to reset Firefox to default setting?

1. Click the menu button and then click help .
2. From the Help menu choose Troubleshooting Information.

   If you're unable to access the Help menu, type about:support in your address bar to bring up the Troubleshooting Information page.

To continue, click Refresh Firefox in the confirmation window that opens.

Firefox will close to refresh itself. When finished, a window will list your imported information. Click Finish and Firefox will open.