After going to full screen, I think I chose view page background or something, scrambling to find some way to get out of full screen. Used Task Manager to exit Firefox. Re-started, same result immediately - back to full screen at the same website. Used Task Manager to exit Firefox. Tried rebooting, and when Firefox started it did the same thing - back to same site in full screen mode. Used Task Manager to exit Firefox. Uninstalled Firefox, re-installed, and when launched, same result. Is there some ini file to clean out? or some history file to clear out? or ...