Start Firefox in Safe Mode. Is there still a problem?

While you are in safe mode; Firefox Options > Advanced > General.
Look for and turn off Use Hardware Acceleration.
Then restart.

Can you attach a screenshot?

• http://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.

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

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

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

You can check for problems caused by a corrupted localstore.rdf file.

• http://kb.mozillazine.org/Corrupt_localstore.rdf

FredMcD - If I start in Firefox Safe Mode, do I lose all my settings? I only have one add-on, Add-Blocker Plus, and a couple of themes. I'd rather not have to hassle with re-enabling it along with resetting all my other settings. Seems like a lot to do just to be able to see the whole customize page. (I don't have this problem any other time.)

Cor-el - Thanks for giving me the link on how to take a screenshot. I always figured it'd be something easy. I hope that I've successfully uploaded it below. I'm curious what the "safe mode start window" will be, and I also need to learn more about "hardware acceleration". I'll study the other links you've provided, esp the one on Safe Mode. I'll let you know if I'm successful.

Looks that the full content of the Firefox window doesn't fit on your screen.

What are the dimensions of your monitor screen?

You can set the layout.css.devPixelsPerPx pref on the about:config page to 1.0 or on Windows 8 to 1.25 and if necessary adjust layout.css.devPixelsPerPx starting from 1.0 in 0.1 or 0.05 steps (1.1 or 0.9) to make icons show correctly.

• http://kb.mozillazine.org/about:config

See also:

• https://support.mozilla.org/kb/forum-response-Zoom-feature-on-Firefox-22

Use an extension to adjust the text size in the user interface and the page zoom in the browser window.

You can look at this extension to adjust the font size for the user interface.

• Theme Font & Size Changer: https://addons.mozilla.org/firefox/addon/theme-font-size-changer/

You can look at the Default FullZoom Level or NoScript extension if web pages need to be adjusted after changing layout.css.devPixelsPerPx.

• Default FullZoom Level: https://addons.mozilla.org/firefox/addon/default-fullzoom-level/
• NoSquint: https://addons.mozilla.org/firefox/addon/nosquint/

The "about:config" suggestion was the ticket! I temporarily set it to 1, made the adjustments I wanted, and reset the config back to the way it was, and my changes remained! Thank you!!