"not responding" means that the CPU is being overworked. 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. A small dialog should appear. Click '''Start In Safe Mode''' (not Refresh). Is the problem still there? '''https://support.mozilla.org/en-US/kb/websites-look-wrong-or-appear-differently''' '''https://support.mozilla.org/en-US/kb/firefox-slow-how-make-it-faster''' '''https://support.mozilla.org/en-US/kb/firefox-uses-too-many-cpu-resources-how-fix''' '''https://support.mozilla.org/en-US/kb/firefox-hangs-or-not-responding''' '''https://support.mozilla.org/kb/Firefox+is+already+running+but+is+not+responding''' ------------ Hi, The people who answer questions here, for the most part, are other Firefox users volunteering their time (like me), not Mozilla employees or Firefox developers. If you want to leave feedback for Firefox developers, you can go to the Firefox ''Help'' menu and select ''Submit Feedback...'' or use [https://input.mozilla.org/feedback this link]. Your feedback gets collected at http://input.mozilla.org/, where a team of people read it and gather data about the most common issues.