BFilter is a smart filtering HTTP proxy. It removes ads,
webbugs, and popups. Unlike the majority of similar tools, it
doesn't rely on a list of blocked URLs, but instead parses HTML
on the fly, and detects ads using a set of heuristic rules.
BFilter has a built-in JavaScript engine which detects popups
and js-generated ads.

WWW: http://bfilter.sourceforge.net