function imageReplacement()
{
  //replaceThem(document.getElementsByTagName('h1'));
  replaceThem(document.getElementsByTagName('h2'));
  replaceThem(document.getElementById('header').getElementsByTagName('a'));
}

function replaceThem(x)
{
  var replace = document.createElement('img');
  for (var i=0;i<x.length;i++)
  {
    if (x[i].className)
    {
      var y = replace.cloneNode(true);
      y.src = 'images/' + x[i].className + '.png';
      y.alt = x[i].firstChild.nodeValue;
      y.title = x[i].firstChild.nodeValue;
      x[i].replaceChild(y,x[i].firstChild);
    }
  }
}

/** 
 * external links
 * sets \target="_blank"\ for all the links with \rel="external"\
*/
function external_links() {
  if (!document.body.getElementsByTagName) return false;
  var as = document.body.getElementsByTagName('a');
  for(var i=0; i<as.length; i++)
    if (as[i].getAttribute('rel') == 'ext')
      as[i].target = '_blank';
  return true;
}