function teaser(what) {
  document.getElementById('teaser_1').style.height = (what==1) ? "240px" : "30px";
  document.getElementById('teaser_2').style.height = (what==2) ? "240px" : "30px";
  document.getElementById('teaser_3').style.height = (what==3) ? "240px" : "30px";
}