Many site issues can be caused by corrupt cookies or cache.

• Clear the Cache

How to clear the Firefox cache {web link}

and

• Remove Cookies

This will log you out of all sites you're logged in to. Press the Alt or F10 key to bring up the tool bar. Followed by;

Windows; Tools > Options Linux; Edit > Preferences Mac; application name > Preferences

Then Privacy. Under History, select Firefox will Use Custom Settings. There is a button on the right side called Show Cookies.

If there is still a problem, Start Firefox in Safe Mode {web link} While you are in safe mode; Press the Alt or F10 key to bring up the tool bar. Followed by;

Windows; Tools > Options Linux; Edit > Preferences Mac; application name > Preferences

Then Advanced > General. Look for and turn off Use Hardware Acceleration.

Poke around safe web sites. Are there any problems?. Then restart.

Try to create a new Boolean pref on the about:config page via the right-click context menu with the name layout.paint_rects_separately and set the value to true and leave hardware acceleration enabled.

You can open the about:config page via the location/address bar. You can accept the warning and click "I'll be careful" to continue.

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