var imgWindow = "";

function openPopup(img, width, height) {
   if (img && width && height) {
      width = Math.min(width + 36, 640);
      height = Math.min(height + 30, 480);
      if (imgWindow.location && !imgWindow.closed)
         imgWindow.close();
      imgWindow = window.open(img, "imgWindow" + width + height, "toolbar=no,location=no,directories=no,status=no,scrollbars=yes,resizable=yes,width=" + width + ",height=" + height);
      imgWindow.focus();
   }
}