Reset Firefox to its default state
- At the top of the Firefox window, click the Firefox button, go over to the Help sub-menu and select Troubleshooting Information.
- Click the Reset Firefox… button in the upper-right corner of the Troubleshooting Information page.
- To continue, click Reset Firefox in the confirmation window that opens.
- Firefox will close and be reset. When it's done, a window will list the information that was imported. Click Finish and Firefox will open.