Better ad blocking starting with Firefox 18.104.22.168
Two patches have been added to Firefox code recently that will improve content blocking as soon as mid May, the estimated release date for Firefox 22.214.171.124.
The patches ensure that content requested by plugins like Flash and Ajax based applications will be subject to the same content policies as regular web pages. So if for example you have asked to block images from server “http://ads.server.net” they will be blocked even if requested by a Flash application or an XMLHttpRequest, one of the core functions used by rich Ajax-based web applications.
Yahoo! Maps, for example, embeds ads in its Flash-based application.