You don't say what the add-on is called, so I can only suggest that you check the menu which usually comes with these add-ons and see if there's an option to disable the popups.

N.B. Please visit the Plugins Check page and update where necessary. Out of date plugins expose your machine to attack.

It was a Facebook Toolbar Add on.

OK, then click the orange Firefox button, go to Add-ons, then Extensions.

The toolbar should be visible in there along with its menu. If it doesn't have a menu, simply remove it altogether and look for an alternative which you can configure.

I don't see the Firefox button.

Wait.. I got it. I went to the Quick Links on the toolbar. And clicked on toolbar settings. THANK YOU!!!!!!!!!

You're welcome.

Could you please click the "Solved It" button next to the post which solved the problem for you? This will help others searching for a solution to the same question.

Thanks.