If you are working with a controlled user base (corporate network or something similar) and can modify browser configuration files/installations, you can configure Firefox 3 to allow developers to hide the location bar. The article below describes the configuration option.
However, as I said before, this functionality was removed (by default) from most, if not all modern browsers as a security precaution. There is no way to guarantee that the address bar will be removed.
http://kb.mozillazine.org/Dom.disable_window_open_feature.location