Avast is ONLY a virus stopper. Pop-ups are (usually) a javascript command to load something... (which may be perfectly harmless)... in a separate box.

Control OF scripts requires code (often other javascript) designed to recognize ad-type javascript and intercept it. What Proxomitron and most other script stoppers do is act as a local proxy and filter all incoming content, then act on it by certain rules. Proxo has levels of rules with many separate rules within each level. Firefox has a similar thing, where YOU add specific rules about what to allow or reject to its adblock extension(s). It's like putting good lock and alarms on your house and perhaps giving a key to trusted people.

Stopping pop-ups does require some tweaking and attention, just as making your home or car safe from break-ins does. The bad guys are constantly looking for ways past the restrictions, so it pays to learn who the good guys are who keep reinforcing the safeguards.