Placing HTML elements on top of the ModalPopupExtender control

If you want a HTML element to always be on top of the ModalPopupExtender control, give the element the CSS z-index value 99999998.

Find the mouse x, y position with JavaScript using jQuery

This is how you find the mouse x, y position with JavaScript using jQuery:

var _mouseX = 0;
var _mouseY = 0;

jQuery(document).ready(function()
{
 $().mousemove(function(e)
 {
  _mouseX = e.pageX;
  _mouseY = e.pageY;
 });
})

The variables _mouseX and _mouseY will at all times have the updated mouse coordinates.