One of the most useful (and quite possibly the most abused) features of JavaScript is its ability to manipulate browser windows. It can be very handy for creating a pop-up navigation.
Multiple pop-up windows can be a real pain, especially now that certain free web space companies are getting in on the act as a method of advertising, so go easy on them. A good rule of thumb is: if you’re opening two new windows, you’re opening one too many!