win.contentTop
var t = w.contentTop
The properties "contentLeft" and "contentTop" contain the actual position
in screen coordinates of the window's inner displayFrame, i.e. the
number of pixels from the top and left corner of the main HTML document. These
values are updated whenever a window is moved or resized.
A common use of these properties is in callback functions for drag boxes
(see User's Guide 3.2). These functions return the corners of the
drag box in absolute screen coordinates. To get the values relative
to the window, subtract "contentLeft" and "contentTop" from them.