Old forum post
ZK Fiddle

A sizable, movable, floatable Panel inside the Center of a BorderLayout will move by the offset of the Center component on every resize.

Check out the Fiddle: The panel's initial position is not (0, 0) already, but its left is equal to the padding around the BorderLayout. Every time you resize the panel it will be pushed down by 23px (height of North) and right by 14px (5px body padding + 9px West width). I guess the Center's offset is not only used to initially position of the Panel, but also added to its top and left every time it is resized.