short: instal https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/ long: it only works on firefox 4.2, the current firefox is firefox 5.0 firefox updated last month i had 4.2 and refused the update and it kept working, but my pc crashed and i had to reinstal firefox the only avaible one on their site was 5.0 so bad luck, look for 4.2, or wait and hope illimutix updates (it also works on chrome 1.0) there might be some tricks to make it work, i a mcurrentmy looking into it http://www.labnol.org/software/old-addons-with-firefox-4/14187/ http://www.webtlk.com/2011/04/25/install-incompatible-old-addons-on-firefox-recent-versions-without-software/ http://www.blogsolute.com/incompatible-addons-firefox-5/17293/ seems that this plugin fixes it https://addons.mozilla.org/en-US/firefox/addon/add-on-compatibility-reporter/