Adblock is the single greatest plugin for Mozilla/Firebird ever made. Properly configured, it will block just about all advertising content on the web. It can block images, iframes, and even javascript content.
It’ll allow you to set your browser to look for certain strings in image URLs which can then be blocked. For example,
*/ads/*
would block anything like:
http://www.doubleclick.com/banners/ads/15.gif
or
http://www.bannermonster/ads/flashcrap.swf
Having something like an */ads/* wildcard will definitely work well, but I’ve found that most ad banners include their dimensions within their filenames. For example, using *480×60* would block any banner with 480×60 in its path or filename, regardless of what directory it’s in or server it’s on.
Once you install AdBlock, you can right-click an offending image to add a block rule to your list. It’s super easy to set up, and it took me like two minutes to configure it with some simple blocking rules. Some good sites to test it out on are:
tomshardware.com
anandtech.com
cnn.com
ign.com
I also messed around with another Mozilla extension, BannerBlind. BannerBlind filters ads by their dimensions and their dimensions only. Unfortunately it didn’t seem to work at all with Firebird!
Prior to finding Adblock I had been using Siemens’ free WebWasher proxy software to block ads, but that thing hasn’t been updated in at least a year. I’m uninstalling that as we speak! One less program to run.