Lately it seems that more and more popups are managing to get through Firefox. It seems that the Macromedia Flash plugin allows webmasters to launch popups in a way that bypasses Firefox’s built-in blocking mechanism. Simply follow these steps to disable this annoyance:

1. Type "about:config" (without the quotes) into the Firefox Address Bar. You may get a warning message, so if you wish to continue, click on the "I'll be careful, I promise" button on the warning page.

2. Right-click on the page and select "New–>Integer"

3. Name the new value "privacy.popups.disablefromplugins" (without the quotes).

4. Set the numerical value to 2