If images are missing then check that you aren't blocking images from some domains.

See:

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

• Check the permissions for the domain in the current tab in Tools > Page Info > Permissions
• Check that images are enabled: Tools > Options > Content: [X] Load images automatically
• Check the exceptions in Tools > Options > Content: Load Images > Exceptions
• Check the "Tools > Page Info > Media" tab for blocked images (scroll through all the images)

There are also extensions (Tools > Add-ons > Extensions) that can block images.

• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

The solution to my problem as stated in this question was resolved by clearing the cache area in Mozilla Firefox. Thanks a million for your help. Now I'm back in business.