WindowElements is an option for Notebook which specifies the elements to include in the window used to display the notebook on the screen.
WindowElements is typically set to a list containing elements such as "HorizontalScrollBar", "MagnificationPopUp", "StatusArea" and "VerticalScrollBar".
The details of particular elements may differ from one computer system to another.
See The Mathematica Book: Section 2.10.13.
See also: WindowToolbars, WindowTitle, WindowFrame.