Navigator 2.0, Internet Explorer 3.0
The close() method closes the top-level browser window specified by window. A window can close itself by calling self.close() or simply close(). In Navigator, if window is the only open window, then close() closes it and Navigator exits.
In Navigator 2.0 and 3.0, there is no meaningful way to close a frame within a window. Thus, the close() method should only be invoked for Window objects that represent top-level browser windows, not those that represent frames.