You can view your Firefox ad blockers by clicking on the Extensions icon on the toolbar (shaped like a puzzle piece). For more settings, view about:addons and click on any ad blocker you want to change the settings of.

Several web sites I've visited recently have complained about my having an ad blocker. I go to the Extensions icon, list the extensions, no ad blocker is listed. I may have had one years ago, the 'memory' of it may be in the system somewhere, but I can't find it.

Any suggestions, other than tossing it all out?