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 also see https://blog.mozilla.org/security/2021/03/23/introducing-smartblock/

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

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}

[v56+] Type about:preferences#general<enter> in the address bar. Under fonts and colors, press the Advanced button. Scroll to the bottom, turn on Allow Web Sites To Choose Their Own.

Make sure you haven't enabled a High Contrast theme in the OS settings.

• We have seen reports that this can be caused by a problem with fonts like Roboto or Helvetica that

you have installed locally and that might be corrupted or are missing some variants. Also, make sure you allow pages to choose their own fonts and that you do not block remote (downloadable) fonts.

• https://support.mozilla.org/questions/1325619 Weird font on some website's

• If you use uBlock Origin make sure not to "block remote fonts".

Check your zoom controls.

<Control> (Mac=<Command>) + (plus) enlarge - (minus) reduce 0 (zero) restore

Make sure you allow pages to choose their own fonts.

• Settings -> General: Fonts & Colors -> Advanced
  [X] "Allow pages to choose their own fonts, instead of your selections above"