function popWindow(url, width, height, windowName, scrollb)
{
    // default width and height for window
    if (!width) { width  = 439; }
    if (!height) { height = 325; }
    if (!scrollb) {scrollb = "yes"}
      // positionering van de popup
      { leftpos=0
        if (screen)
           {
            leftpos = screen.width-(width+230)
           }
      // als de windowname niet is gelukt
      if (!windowName) { windowName = "thispopup"; }
      wref = window.open (url, windowName,"toolbar=no,width=" + width + ",height=" + height + ",directories=no,status=no,scrollbars=" +scrollb + ",resizable=yes,menubar=no,top=50,left="+leftpos);
      wref.focus();
      }
    }