Many times we run across Firefox extensions which are are not compatible with the version that we are using. But there's always a workaround. Two of them actually. The first one - Type about:config into Firefox 's address bar and click the "I'll be careful, I promise!" button. Right-click anywhere. Choose New>Boolean . Make the name of your new config value extensions.checkCompatibility and set it to false . Make another new boolean pair called extensions.checkUpdateSecurity and set the value to false . Restart Firefox . The second one - Download the *.jar , *.xpi file. Open the file with WinRAR . Look for the file install.rdf . It contains the information about which versions of Firefox it is compatible with. Edit the file in Notepad . For that you may have to copy the file to hard disk, edit it,save it, then copy it back to the file with WinRAR . Change the x.0.0.* in < em:maxVersion > x.0.0.* < /em:maxVersion > to 4.0.0.* or any high