I'm too lazy to look for the original thread (so apologies in advance to whomever I'm quoting without crediting), but I did email the instructions to myself at the time, so here they are:
Step 1: If you don't have Firefox already, get it here. Configure it, etc.
Step 2: Download these 2 extensions in Firefox after installing the browser -
AdBlock 0.5.2
ChromEdit
Step 3: Restart Firefox, then click on Tools - Adblock - Preferences
Step 4: Add 3 new filters:
http://images.neopets.com/buttons/*
http://images.neopets.com/728ads/*
http://images.neopets.com/ads/*
Click Add button to save them. Then click done.
Step 5: Go to Tools - Edit User Files, then click on the userContent.css tab.
Step 6: Scroll all the way to the end, then enter a new line:
#ban { display: none !important; }
Click the Save button.
Step 7: Restart Firefox and enjoy an ad-free NeoPets experience
Now, this does
not work with the most recent version of Firefox, because ChromEdit is not compatible. I recently went looking for a fix, and found this...
download the .xpi, rename to .zip, unzip install.rdf and edit max field to be 2.0 or whatever, put the file back into the zip and rename back to .xpi, drag & drop to firefox and you're set.
... but so far I can't get it to work. If anyone is technically minded and cares to explain it, the bit I'm stuck on is "drag & drop to firefox." I can't work out where it goes.
Hope this is vaguely useful.