//Specificaties in popup:

 var myWindow = null;
  function closeMyWindow() {
    if (myWindow && !myWindow.closed) {
      myWindow.close();
      myWindow = null;
    }
  }
  //Parameters url, width, height (eventueel nog scrollbars toevoegen)
  function ow(url,w,h) {
    var width=w;
    var height=h;
    if (!window.open) return true;
    closeMyWindow();
    var x = (screen.width -width) >>1,
        y = (screen.height-height)>>1;
    myWindow = window.open(url,'popWin',
      'width='    + width +
      ',height='  + height +
      ',left='    + x +
      ',top='     + y +
      ',screenX=' + x +
      ',screenY=' + y +
      ',scrollbars=yes');
    myWindow.focus();
    return false;
  }