Hi, open the 3-bar menu > Add-ons > Extensions, and look for/remove/disable anything you don't recognise then restart Firefox. Look in your PCs programs for anything recently installed that you don't recognise. Delete ALL references to the website in question. To do that, open the 3-bar menu > Library > History, then click the Show All History link at the bottom of the list to open the History-library window. Search for the website you want to clear by typing its name in the Search History field in the top-right corner. Now in the search results, right-click on the site you want to remove, and select Forget About This Site. (Browsing and download history, cookies, cache, active logins, passwords, saved form data, exceptions for cookies, images and pop-ups for that site will be removed). (Give it a few minutes to complete the deletion.) More - [[Delete browsing, search and download history on Firefox]]. You can try these free programs to scan for malware, which work with your existing antivirus software: * [https://www.microsoft.com/en-us/wdsi/products/scanner Microsoft Safety Scanner] * [http://www.malwarebytes.org/products/malwarebytes_free/ MalwareBytes' Anti-Malware] * [http://support.kaspersky.com/viruses/disinfection/5350 Anti-Rootkit Utility - TDSSKiller] (for more info, see this [https://www.bleepingcomputer.com/download/tdsskiller/ alternate TDSSKiller download page]) * [https://www.malwarebytes.com/adwcleaner/ AdwCleaner] (for more info, see this [http://www.bleepingcomputer.com/download/adwcleaner/ alternate AdwCleaner download page]) * [http://www.surfright.nl/en/hitmanpro/ Hitman Pro] * [http://www.eset.com/us/online-scanner/ ESET Online Scanner] '''Note that not all removal programs will detect all malware, so you may need to run several or all of them.''' Further information can be found in the [[Troubleshoot Firefox issues caused by malware]] article. Did this fix your problems? Please report back to us. Thank you!

Thanks, I found a web page in the history from the site causing the problem. I've deleted it and the problem seems to have gone away. What I don't understand is how a web page, that I apparently visited in the previous 7 days, that I don't ever remember visiting (and now appears to be unavailable) can be trying to connect to the internet. Regardless. Thanks for your help.

I had this problem too and followed the instruction. How can I be shure that the crab is gone? The popup of Norton does not show up anymore but I am just not shure if it's gone.