When Firefox blocks a popup a yellow bar should appear at the top of the content area of the window. See the screen shot here. <br /> https://support.mozilla.com/en-US/kb/Pop-up+blocker#What_are_Pop_ups_ If you are getting a different type of message you might have another popup blocker on that PC, like part of a Security Suite. If that is the case, you should turn-off that 2nd popup blocker and let Firefox do its' thing.