Why do you need this, you shouldn't create it. Rated 1 out of 5 stars

There's an addon called Adblock Plus. It blocks those ads. Arfcom ad blocker can't really do that.

Rated 1 out of 5 stars

Some instructions would be nice.
I assume you configure this thing by going to Tools > Add-ons and clicking the Preferences button in the listing for Arfcom Ad Blocker.
Unfortunately, the Preferences button is grayed-out. I'm running Firefox on Ubuntu 7.10.

Possible bug? Not yet rated

There's a particularly annoying bug that occurs in Firefox when Arfcom Ad Blocker is enabled, that goes away when it's disabled.

Here's an example page which doesn't render correctly when this extension is enabled:

Possible bug in Firefox version with Arfcom Ad Blocker

This text appears.

This text appears too.

After a refresh, this text appears momentarily, then disappears.
  The bug appears to be related to "Arfcom Ad Blocker";
since the bug disappears when the extension is disabled.

Crap Not yet rated

There is already Adblock Plus, if you haven't realised, and it BLOCKS those ads. If it doesn't, you can easily and manually block them.

The spectrum of this addon is as narrow as a hair

adblock Rated 1 out of 5 stars

Adblock will block what ever you want it to if you know how to use it.

www.sample.com* (blocks site completely)
www.sample.com/ads* (only blocks url with 'ads' included)
www.sample.com/ads/ad.jpg (blocks that image only)

Blocks more than ads Rated 2 out of 5 stars

Installed Ad Blocker, but had to uninstall as it also blocks items that are not ads.