function close_teaser(id) {
  display = document.getElementById('teaser_content_'+id).style.display;
  if(display == 'none') {
    document.getElementById('teaser_content_'+id).style.display = 'block';
    document.getElementById('close_button_'+id).className = 'teaser_close';
    document.getElementById('close_button_'+id).innerHTML = 'zusammenklappen';
  } else {
    document.getElementById('teaser_content_'+id).style.display = 'none';
    document.getElementById('close_button_'+id).className = 'teaser_open';
    document.getElementById('close_button_'+id).innerHTML = 'aufklappen';
  }
}