That could be the 'alt' attribute for images that are blocked or otherwise not displayed.

• https://support.mozilla.org/en-US/kb/fix-problems-images-not-show
• https://support.mozilla.org/en-US/kb/websites-look-wrong-or-appear-differently

If that is normal text then it can be caused by setting a higher default minimum font size.

If you have made changes to Advanced font-size settings like increasing the minimum/default font-size then try the Default font-size setting "16" and the Minimum font-size setting "none" in case the current setting is causing the problem.

• Options/Preferences -> General: Fonts & Colors -> Advanced -> Minimum Font Size (none)

Make sure you allow pages to choose their own fonts.

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

It is better not to increase the minimum font-size, but to use the builtin Firefox Zoom feature.

• Options/Preferences -> General -> Language and Appearance -> Zoom

This helped, it corrected the Youtube titles so they don't over lap, it was the "Give Firefox a tune up"--"Refresh FireFox" that fixed the webpage display problem.

What is still not fixed, is my Thunderbird display,
I still have overlap in some parts of emails that are ads,
like the Newegg ad I showed in my first post.
Thanks for the help.

I have no idea why the font changed, it was fine at writiing, but when posted it is wonky.