function CenterPopup(url,popW,popH) {
  var w = 640, h = 480;

  if (document.all || document.layers) {
   w = screen.availWidth;
   h = screen.availHeight;
  }

  var lpopW = (popW+20);
  var lpopH = (popH+40);
  var leftPos = (w-lpopW)/2;
  var topPos = (h-lpopH)/2;
  contentPopup = window.open(url,'CenterPopup','width=' + lpopW + ',height=' + lpopH + ',top=' + topPos + ',left=' + leftPos + ',toolbar=no,location=no,directories=no,menubar=no,scrollbars=no,status=no,resizable=no');
}