Where & When do you see this message??

Does this message appears when you try to access some website ??

• If yes then on what website does it appear ??

I have noticed it most while on eBay. I often have to go back and forth between a listing of items sold, where I contact the Buyer, then Back Page to the listing again. That's when the popup message will show. I'm not on enough other sites to notice if it repeats there, but I believe that it has happened on other sites, too.

Perform the suggestions mentioned in the following articles:

• Clear Cookies & Cache
• Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems

Check and tell if its working.

May not be related to your problem but some of your Firefox Plugins are out-dated

• Update All your Firefox Plugins -> https://www.mozilla.org/en-US/plugincheck/
• When Downloading Plugins Update setup files, Remove Checkmark from Downloading other Optional Softwares with your Plugins (e.g. Toolbars, McAfee, Google Chrome, etc.)

I notice this happening with certain search result pages. I'll do a search, follow a link, then go "back" to the search results page, and Firefox will not display the page, instead generate the message. This is new to 10 or 11. Issue reproduces after cache clear and cookie removal. I haven't tested extensions, but I can't imagine that Adblock or mousegestures are at all related.

This is a change in firefox's behavior since version 10. If you try to go back to a page that's the result of submitting a form and isn't stored in the cache, you'll get this error.

Currently, the only 'fix' is to revert to version 9 or earlier. However, given the number of people annoyed by this behavior, it's likely somebody will eventually create an extension to fix it.