Firefox's built-in popup blocker is designed to prevent sites from opening new windows if you have not taken any action on the page. However, that's a pretty liberal definition, so you still can get some popups from time to time.

A more serious problem is that some add-ons may open popups. You might not even realize you have them, if they snuck onto your system with some free software you downloaded. 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 change things?

If you have installed any free software (other than avast!), it's possible it was bundled with some malware.

It's a good idea to check the Control Panel, Uninstall a Program, and click the "Installed on" column heading to group additions by date. This often reveals unexpected items that you can remove.

To mop up, you can supplement avast! with some of the tools other Firefox users have found helpful: Troubleshoot Firefox issues caused by malware.

hmmm, yeah no add ons at all. this is a brand new pc as of yesterday and the problem started yesterday. even with mcafee which comes pre installed didnt catch the issues. The only add on and extension on fire fox at the moment is the avast. When i installed avast, i used custom install and made sure that no other programs were installed.

This is not just a add once in a while but every page, including goolge, has pop ups now and spy bot has found nothing, mcafee has found nothing nor has avast...

This is a fresh brand new pc from HP. very strange that it is doing this. Its like windows 8.1 is not doing what it was supposed to do..

of all the pc's i have built, this is the first time this has ever happened. I have always used firefox and i doubt it is firefox doing it, i believe it is a windows 8.1 issue hidding deep in a cave....

Could you check your download history to see where you installed Firefox from? Unfortunately, a number of unofficial bundle versions are out there which can contain a lot of annoying extras.

Ok, so i think i figured it out. I used ADWcleaner and it found affpackages on my pc, cleaned it and so far no adds. NOW, my issue is that every time i right click on ANYTHING, it goes super super slow. takes about 3 min for right click menu to pop up. haha. but i am fixing that via another forum. So mark this thread as resolved and make sure that people can read this thread becasue it was annoying to have that on the first day of the new laptop.