The pop-up may not actually be coming from Firefox. Pop-ups not being blocked Is the pop-up coming from Firefox? For more information, see the What are Pop-ups? section above. Note: Blocking pop-ups may not always work and may interfere with some websites.
Pop-up windows, or pop-ups, are windows that appear automatically without your permission.
3.3 Is the pop-up shown after a mouse click or a key press?.3.2 Is the pop-up blocker on and enabled for this site?.