Make sure that you do not block JavaScript

Reload web page(s) and bypass the cache to make sure to get the latest versions of all files.

• Press and hold Shift and left-click the Reload button.
• Press "Ctrl + F5" or press "Ctrl + Shift + R" (Windows,Linux)
• Press "Cmd + Shift + R" (MAC)

Start Firefox in Use Troubleshoot Mode in Firefox 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

It cured itself by the next afternoon. I did not take any of the steps in the email as it had cured itself. I wondered if it was the 24 to 48 to fully shift a web site from server to another server.

Items stored in the cache may have expired and made Firefox retrieve new data from the server.
If you make changes to the code or files on your own website or suspect that some one else did on their website then always first try to reload the page and bypass the cache like I wrote above to refresh al files.
In case of some media files you may need to clear the cache to make it work.