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).

Is the problem still there?

Start your Computer in safe mode with networking. Then start Firefox. Try Safe websites. Is the problem still there?

Starting The Computer In Safe Mode;
Free Online Encyclopedia

mrmodo said

Been using firefox for a long time. It is now stopping and becoming non responsive for 10-15 seconds if you switch between tabs or go back using the back button. It does this regardless of HP, Acer or Dell pc's or laptops. It is also consuming huge portions of memory and disk i/o. What gives and how can this be improved. versions are the latest from mozilla. help please. mrmodo

although it does not pause with the (not responding) message, it is still very very slow. Compare to Chrome, or even Edge, they are both much faster returning to the page with the back button. web sites have this issue are all sites but the worst one is MSNBC and CNN. Other news sites are just as slow (WSBTV) etc. There has to be an internal code issue clearing core for page refresh as these are not new pages just going back to the previous page. This also includes email pages such as yahoo.com.

One cannot bring up Mozilla/Firefox continuously in safe mode. It requires a fix.

Safe Mode is a troubleshooting mode that temporarily turns off hardware acceleration, resets some settings, and disables add-ons (extensions and themes). If the problem goes away, that tells us one thing. If it does not, that tells us something else.

safe mode is not the answer. I am a pc and development person. Safe mode only improved the process slightly. This problem is on every pc with firefox and does not occur with Chrome or Edge. All items have been disabled with no POSITIVE results. Has to be a coding issue within Firefox

Please create a new Profile, just for baseline testing purposes. Don't do anything with your current Profile. https://support.mozilla.org/en-US/kb/profile-manager-create-and-remove-firefox-profiles

the replacement of the default profile has made the firefox brower much much faster. I think this did it.

Thanks

You're welcome!

Are you aware of this support article which tells you how to transfer important data files from the old Profile to the new Profile? https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile#w_copying-files-between-profile-folders