A reference to the Window object that opened this one, or null if this window was opened by the user.
parent
If the current window is a frame, a reference to the frame of the window that contains it.
self
A self-referential property; a reference to the current Window object. A synonym for window.
top
If the current window is a frame, a reference to the Window object of the top-level window that contains the frame. Note that top is different from parent for frames nested within other frames.
when u meet a unknow parameter of Javascript.
First step,search the web.
Second,read JavaScript.The.Definitive.Guide.4th.Edition and then write some codes to practice.
The last,go to a forum and post a new thread for your question.