Is this with all websites/pages, some, a few?

Make sure you are not blocking content.

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there?

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}

Looks like a problem with a High Contrast Mode.

See 'New':

• https://www.mozilla.org/en-US/firefox/91.0/releasenotes/

Firefox now automatically enables High Contrast Mode when "Increase Contrast" is checked on MacOS

Fred, it seems to be all websites...Yahoo, Facebook, Google Drive, my workplace...everything I've tried so far.

The problem is still there when I go into safe mode.

I tried clearing cookies and the cache as you said, but no change in the appearance of pages afterward.

Any other thoughts?

Core-El,

My computer did update Firefox yesterday to the new version...no problems then or this morning, but perhaps it did not take effect until I rebooted my computer this afternoon.

I see what you're referring to on that link about High Contrast Mode. What do you think I need to do about that if it's the issue?

Thanks!

If I uncheck my "Increase Contrast", that does resolve the problem. Excellent suggestion!

I suppose I will do that for now and hopefully not notice the difference. Not sure if there is a way to use it again without causing the problem.

Thank you both for your quick replies.

Facebook and some other sites weren't displaying correctly for me after the update to 91.0. In Firefox, I set the option in Colors (in Fonts and Colors): "Override the colors specified by the page with your selections above" to Never. That allowed me to keep my Mac's Increase contrast on (and with it Reduce Transparency) in my OSX's settings. (OS 11 really).

Facebook now looks as it should and I don't have to lose any of my preferred Mac settings.

This is my response to the feature "Firefox now automatically enables High Contrast Mode when "Increase Contrast" is checked on MacOS.", new with 91.0.