You can start Firefox in Safe Mode to check if one of the extensions (Firefox/Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/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

The problem still occurs in Safe Mode. The message reads "You must have Javascript turned on ...".

You can check the javascript.enabled pref on the about:config page via the location bar.

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

You can check for problems with preferences.
Rename or delete the prefs.js file and possible numbered prefs-##.js files and a possible user.js file to reset all prefs to the default value.

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/Resetting_preferences

These files are hidden to me because my OS/X is 10.8.4 and I cannot make them appear. This is way, way more trouble than it's worth. Thanks for your help. Firefox has lost me.

In Mac OS X v10.7 and later, the $HOME/Library folder is a hidden folder.

Open Finder and use one of these:

• Go > Go To Folder (Shift-Command-G) and in the dialog type: ~/Library
• Open the "Go" menu and hold down the Option key to make the Library appear

• http://kb2.adobe.com/cps/909/cpsid_90947.html Access hidden user library files

See also:

• http://kb.mozillazine.org/Show_hidden_files_and_folders