function th_galerie(node)
{
  var thumbs = node.parentNode.childNodes;
  for (var i=0; i<thumbs.length; i++)
  {
    if (thumbs[i].tagName == 'A')
    {
      thumbs[i].className = '';
    }
  }
  var newImg = node.childNodes[0].getAttribute('src');
  document.getElementById('gal_gross').setAttribute('src', newImg);
  node.className = 'aktiv';
}