DragPanelExtender Server Reference
This extender attaches the stock "floatingBehavior" to a Panel, and is an example
of wrapping an existing behavior with an extender.
When attached to a Panel, the user can then drag that panel around the browser rendering surface
using the mouse.
DragPanelExtender Server Properties
The server ID of a control that will serve as the "handle" for this drag operation.
When the user clicks and drags on this control, the associated panel will be moved as well.