I've used Firefox for years. Google ads usually show up in my web pages when I'm browsing. Recently they stopped showing and I couldn't figure out why. I checked my Firefox Tools>Addons>Extensions and there was no sign of Adblocker software. I am writing this question so I can post the answer for anyone else with this problem. I'll post the answer here, just in case I have a problem trying to reply to my own question: If you have recently installed Avast antivirus software you may have installed Adblocker without adding an icon to Firefox and without knowing you've installed it. (like me!) If you have Avast, click on its icon (a green circle, orange number thing) in the top right side of the Firefox screen. When the Avast window opens, at the bottom it should say "My Avast" and "Settings" Click on "Settings" In the new window, find the item that says Block ad tracking by default, and click to remove the check mark. Click on the Save button. I hope this helps someone else like me who was confused by it for a while.