What is your computer system and Firefox? What is the full error messages you are getting? '''[https://www.mozilla.org/en-US/plugincheck/ Use this link to check that your plugins are up-to-date.]''' If any are listed as unknown or research, do not worry about them. ---------- Start '''[https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode Firefox in Safe Mode]''' {web Link} by holding down the '''<Shift><br> ''(Mac=Options)'' ''' key, and then starting Firefox. Is the problem still there?