if(document.images) {
  Bild = new Image();
  Bild.src = "images/startseite2.jpg";
}

function img_swap() {
  if(document.images) {
    document.images.start.src = Bild.src;
    document.getElementById("link").href = "";
    document.getElementById("link").style.cursor = "default";
    return false;
  }
}