I had no problem with https://health.clevelandclinic.org/ Many site issues can be caused by corrupt cookies or cache. * Clear the Cache and * Remove Cookies '''Warning ! ! ''' This will log you out of sites you're logged in to. You may also lose any settings for that website. * '''Cookies; ''' [https://support.mozilla.org/en-US/kb/delete-cookies-remove-info-websites-stored Delete cookies to remove the information websites have stored on your computer] {web link} * '''Cache; ''' [https://support.mozilla.org/en-US/kb/how-clear-firefox-cache How to clear the Firefox cache] {web link} If there is still a problem, '''[https://support.mozilla.org/en-US/kb/troubleshoot-firefox-issues-using-safe-mode Start Firefox in Safe Mode]''' {web link} by holding down the '''<Shift> ''(Mac=Options)''''' key, and then starting Firefox. A small dialog should appear. Click '''Start In Safe Mode''' (not Refresh). Did this help? While you are in safe mode; Try disabling graphics hardware acceleration in Firefox. Since this feature was added to Firefox it has gradually improved but there are still a few glitches. ''[https://support.mozilla.org/en-US/kb/forum-response-disable-hardware-acceleration How to disable Hardware Acceleration]'' {web link}

It worked in Safe Mode. By disabling each add-on one by one, I found the bad one: Privacy Badger. I think this one tries to defeat trackers. Clearing the cache, cookies did not remove the problem. Problem solved.

That was very good work. Well done. Please flag your last post as '''Solved Problem''' so others will know.