How To Refresh Mozilla Firefox
If Firefox is causing problems it may be necessary to refresh to restore to factory default settings.
There are several ways to accomplish this.
This KB Article Describes the process and provides a Refresh Button.
Firefox Reset KB Article
First try the Blue Refresh Button while logged on to the computer with Firefox issues.
If that is not successful per the above article restart Firefox in Safe Mode. You have the option to refresh.
Firefox Safe Mode Start Up
If Firefox won't start you can do a manual refresh by creating a new profile and transferring your important data to the new profile.
How To Create New Firefox Profile and Trafer Data To IT.