function openWindow(adr,props) {
  fenster1 = window.open(adr, "popup", props);
  fenster1.focus();
}


function rollover(id) {
  kachel = document.getElementById(id)
  switch (kachel.className) {
  case 'lightgrey':
    kachel.className = 'green';
    break;
  case 'green':
    kachel.className = 'lightgrey';
    break;
  }
}