Message (in red) says it's been disabled (unsigned add-on). I performed the following instructions to be able to use unsigned add-ons, but that didn't correct the problem. 1) typed: about:config 2) searched for: xpinstall.signatures.required 3) Double clicked the preference, setting it to "false" Every ad blocker add-on, fails. 1) Why didn't changing the preference work? 2) What signed add-on is available to use? Thank you for any assistance you can provide.