Does it seem related to scrolling? Here are some suggestions for dealing with display aberrations:

Could you try turning off a few Firefox settings. I'm not sure whether you need all of these, but no single one seems to solve the issue for everyone.

You usually need to restart Firefox in order for these changes to take effect, so save all work first (e.g., mail you are composing, online documents you're editing, etc.).

Edit > Preferences > Advanced > General > "Browsing" section

Uncheck the first 3 boxes:

1. Use autoscrolling
2. Use smooth scrolling
3. Use hardware acceleration when available

If you OK that and restart Firefox, is the issue resolved?

I did the three changes you suggested, exited Firefox and then opened Firefox again and tested at the web site that was the culprit. That seemed to work! It is good to get things back to normal. I would like to hear what the actual problem was if you will. :-)

Once again, thanks a million for the assist.

OOPS! I saw the problem again at this web site after navigating

           to the forum section (???).

I'm not sure why smooth scrolling (switched on in Fx13) creates problems for some users; the hardware acceleration issues are glitches with particular graphics card drivers that apparently are hard to debug.

Can you see a pattern to when it happens and maybe post a screen shot (using your OS or a digital camera)?

Start Firefox in Safe Mode to check if one of the extensions or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance/Themes).

• Don't make any changes on the Safe mode start window.
• https://support.mozilla.org/kb/Safe+Mode

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