Does it still happen in Troubleshoot Mode?

You might need to upgrade/downgrade your graphics drivers or work around it by disabling hardware acceleration.

It still happens in Troubleshoot Mode.

Altering graphics driver/disabling acceleration doesn't help, either.

It seems to not happen in "Private Mode."

Not really sure if this problem is solved or not.

All this started with the most recent FF update.

FURTHER, after recent update, FF imported very old bookmarks into the "Bookmarks Toolbar." Why??

Recent updates have also changed my privacy settings without my consent.

I've been using FF since single digit versions.... Not very pleased with FF these days :-(

You can try these steps in case of issues with webpages:

You can reload webpage(s) and bypass the cache to refresh possibly outdated or corrupted files.

• hold down the Shift key and left-click the Reload button
• press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• press "Command + Shift + R" (Mac)

Clear the Cache and remove the Cookies for websites that cause problems via the "3-bar" Firefox menu button (Settings).

"Remove the Cookies" for websites that cause problems:

• Settings -> Privacy & Security
  Cookies and Site Data: "Manage Data"

"Clear the Cache":

• Settings -> Privacy & Security
  Cookies and Site Data -> Clear Data -> [X] Cached Web Content -> Clear

• https://support.mozilla.org/en-US/kb/clear-cookies-and-site-data-firefox
• https://support.mozilla.org/en-US/kb/how-clear-firefox-cache

Start Firefox in Troubleshoot Mode to check if one of the extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) or if hardware acceleration or if userChrome.css/userContent.css is causing the problem.

• switch to the Default System theme: "3-bar" menu button or Tools -> Add-ons -> Themes
• do NOT click the "Refresh Firefox" button on the Troubleshoot Mode start window

• https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

• https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop
• https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection
• https://support.mozilla.org/en-US/kb/trackers-and-scripts-firefox-blocks-enhanced-track

You can remove all data stored in Firefox for a specific domain via "Forget About This Site" in the right-click context menu of an history entry ("History -> Show All History" or "View -> Sidebar -> History").

Using "Forget About This Site" will remove all data stored in Firefox for this domain like history and cookies and passwords and exceptions and cache, so be cautious. If you have a password or other data for that domain that you do not want to lose, make sure to backup this data or make a note.

You can't recover from this 'forget' unless you have a backup of involved files.

If you revisit a 'forgotten' website, data for that website will be saved once again.

• https://support.mozilla.org/en-US/kb/delete-browsing-search-download-history-firefox

With all due respect, this is more trouble and more complicated than I think it should be. I'm really not willing to go through all these steps, as they are WAY beyond my comfort level.

It still happens in Troubleshoot Mode. It seems to not happen in "Private Mode."

Clearing cookies/storage for the site should easily fix it then.

Sorry, didn't work.

I'll be trying a different browser....

Does it still happen in a new profile? An easy way to test a new profile is to install Developer Edition and see if it happens there or refresh your existing profile.

More than I'm willing/able/comfortable to do.

To be clear, this problem is not necessarily solved. I'm just going to go to Chrome and not follow this convo anymore.

Mozilla needs to stop issuing so many updates and forcing "new" features on users.

Thx..