To use this script, you need the Firefox-Plugin "Greasemonkey", which you can find at http://www.greasespot.net/ or the usual Firefox addons page (Tools->Addons->Get Extensions). Once you have Greasemonkey installed, you can install the "Block" script from here (http://userscripts.org/scripts/show/13290, click on the install button to the right).

After installation of this script, you also have to add the pages you want it to run on (Tools->Greasemonkey->Manage User Scripts).

Please leave suggestions for improvements in the comments.