By using JavaScript, a web site may open additional windows to display ads or other content. In some cases, this might be useful. (A "remote control" feature, for example.) However, in most cases, it's used to annoyingly display ads. In some cases, it's used along with the "Un-Load" trick (from a following test) to open up one or more windows for each one you close, thus trapping you in what can be affectionately called "pop-up hell." This test will see how your browser would react to the JavaScript function used to make a pop-up Window.