unwanted popups

In a Firefox window, the left-most pane shows Homepage on top followed by a list of recent open websites. In my current window for example, below the home page heading I have Log in/Sign up/Mozilla Support then Get Support| Mozilla Support followed by +New Tab. There is nothing special about the particular configuration. I mention the exact configuration for orientation. My problem, for the example I am describing, is the existence of a popup that is in a separate bubble window that states Get Support|Mozilla Support on the first line and support.mozilla.org in the second. Popups like this one always appear. They are driving me crazy because they persist when some new window is moved over the Firefox window. That is, they always come to the front of a stack of windows. They often cover some clickable list in another application. I'm working with the latest MAC OS on a Macbook Pro. I have tried the usual advice to turn off popups in the FireFox settings. This toggle has no effect on these popup windows. Is there a way to turn them off!