Browser popup window has been a hot topic for few years now. There are sites that shamelessy open popup windows without asking your permission and even making those windows virtually impossible to close. Other sites have a more descent policy and they actually warn you about popups that they use or even give you an option to open link in a current window.
Because of so many sites abusing popup window technology, many browsers (like Mozilla) started to add popup blocking functionality. There are also standalone applications that limit the amount of nerves you lose while browsing.
PopupTest is the site that allows you to test how good your popup blocking software works. Many different technologies are implemented there. I have tried all of those with FireFox 0.8 and found that only three types of popups can get through to me – mouseOver, drop down, and sticky. I don’t know if it is possible to configure FireFox to block those, but I don’t mind much, since these are rear for the sites I visit.