Right under Popup Windows, you'll see a checkbox that should be ticked; "Allow Web Sites to Install Software."
- I recommend that you keep that little box checked, as there are certain websites that will need to install (harmless) software on your machine in order to run like they should. Check on the Allowed Sites box to see if there's anything in there. You should only see Mozilla sites (which makes sense. If you see anything else that you're not familiar with, I would click "Remove Site" and run a virus check on your computer. Just to be safe.
- blocks third-party images, such as ads.
- cuts down on imagery theft; for example, some sites will just link directly to another site's images, stealing their bandwidth without their permission.
