Hi Tomas,
There is no direct support on this, one way you can do it is by dealing with the DHTML directly:
Code: JavaScript
var element = document.getElementById("dialog1");
var x = element.offsetX;
var y = element.offsetY;
Such code will give you the location of the dialog relative to its first positioned parent element. You can then save it on your server side. When you need to apply these values again on the server side, set the dialog's AnchorElementID, OffsetX and OffsetY property. Note you may need to adjust the value that you get from client side based on which element you use for anchor.
Thanks