Using window Objects
At the top of the browser object hierarchy is the window object, which represents a browser window. You've already used a few methods and properties of the window object:
You used the window.status property to change the contents of the browser's status line.
The window.alert, window.confirm, and window.prompt methods display message dialogs to the user.
There can be several window objects at a time, each representing an open browser window. Frames are also represented by window objects. You'll learn more about windows and frames in Hour 11, "Using Windows and Frames."
Layers, which allow you to include, modify, and position dynamic content within a Web document, are also similar to window objects. These are explained in Hour 19, "Using Dynamic HTML (DHTML)."