.PopupFrame
{ 
  display: none;
  position: absolute;
  background: white;
  border: 1px solid black;
}

.PopupFrame .CloseButton
{
  position: absolute;
  top: 5px;
  right: 25px; 
  width: 14px;
  height: 14px;
  background: url(../images/close_window.gif) 50% 50% no-repeat;
  border: none;
}