Firefox's built-in popup blocker is designed to prevent sites from opening new windows if you have not taken any action on the page. However, that's a pretty liberal definition, so you still can get some popups from time to time. A more serious problem is that some add-ons may open popups. You might not even realize you have them, if they snuck onto your system with some free software you downloaded. Try this: Disable ALL nonessential or unrecognized extensions on the Add-ons page. Either: * Ctrl+Shift+a * orange Firefox button (or Tools menu) > Add-ons In the left column, click Extensions. Then, if in doubt, disable. Usually a link will appear above at least one disabled extension to restart Firefox. You can complete your work on the tab and click one of the links as the last step. Does that change things?