This may be from another Firefox extension, which Adblock Plus might not be able to block. Try this:

Disable ALL nonessential or unrecognized extensions on the Add-ons page. Either:

• Ctrl+Shift+a
• orange Firefox button (or Tools menu) > Add-ons

In the left column, click Extensions. Then, if in doubt, disable.

Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step.

Does that stop it?

Not all extensions can be removed from the Add-ons page. Some need to be removed using the Windows Control Panel, Uninstall a program, or physically if there is no uninstaller. If you have suspicions about or difficulty removing particular extensions, please name names and we can try to determine now best to get rid of it.

Finally, unwanted software often arrives in a bundle. Supplement your regular security scans with some on-demand tools such as the ones listed in this support article: Troubleshoot Firefox issues caused by malware.

You may also want to check your connection setting, in case your Firefox connection is being diverted from its normal path.

orange Firefox button (or Tools menu) > Options > Advanced > Network mini-tab > "Settings" button

The default is "Use system proxy settings" which should use the settings you can adjust from within Internet Explorer, but you might also try "No proxy" to see whether that helps.

yes, that's usually a sign of adware active on your pc - also see this similar question: /questions/982924

Thank you all for your replies. Luckily I finally managed to get into contact with the ad provider itself and was able to resolve the issue. Apparently the thing had installed itself onto my computer without my knowledge, so I promptly (and happily) uninstalled it.

Again, thanks for the advice!

I have a similar problem, different ads, though....is there any point in you telling me HOW you uninstalled it? I am a non-techie, and this is driving me nutso, too!. Kind regards, Sylvia

Hi Sylvia, did you try the steps listed in this thread?

Hey Sylvia,

This is what worked for me: Go to control panel and click programs and then uninstall programs. If you know the name of the ad carrier who's polluting your computer you can find it in there. Typically they sneak in as part of bundle downloads and you don't even know you have them. On my computer (windows) the image/icon for stupid ad carriers in the programs typically looks like a grey trash can (quite appropriate in my opinion). You find it, right click it, and press uninstall. That's what saved my sanity - works every time!

Hope this helps!

Sorry, I tried this & there were no programmes installed....so I got an adware removal tool, Anti virus thingy....that eventually got rid of it... I ended up installing Avast, uninstalled Avira, & am now running Avast alongside Malware Bytes, all seems to be ok at this time. I run updates & scans daily, still trying to hang on to WIN XP for as long as I can, I am saving for Windows 8.... Thanks for your time, though & trying to help me, I really appreciate it.... Peace & Love Sylvia