Did you possibly install a lightweight theme (Persona)?

Start Firefox in Safe Mode to check if one of the extensions (3-bar Menu button/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem.

• Switch to the DEFAULT theme: 3-bar Menu button/Tools > Add-ons > Appearance
• Do NOT click the "Refresh Firefox" button on the Safe Mode start window

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

Can you attach a screenshot?

• https://en.wikipedia.org/wiki/Screenshot
• https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem

• Use a compressed image type like PNG or JPG to save the screenshot
• Make sure that you do not exceed the maximum size of 1 MB

Thanks for your excellent two replies. Safe Start eliminates both problems, so I'm assuming that it is indeed a squabble among add-ons.

I've taken four screenshots - Normal Start_JWP.png, Safe Start_JWP.png, and two of the full list of add-ons, Add-Ons_1.png and _2.png Will try to attach all to this response. If it fails, I'll send the four individually.

Thanks in advance for your attention!

--- John

Try the Options button for Old Location Bar, Style panel, for the yellow color. Not sure where the green is coming from.

Hi - Thanks for trying, but that's not the solution. Can't get rid of yellow for secure sites though it was never checked in Old Loc Bar options. --- John

Well... you are in the best position to check Options or try disabling individual extensions since you already have that set of them installed.