function replaceTitlesInit()
{
  /* Check for DOM support */
  if (!(document && document.implementation && document.implementation.hasFeature))
    return;
    
  /* Check for image support */
  if (!document.images)
    return;
    
  /* Tags to be replaced */
  replaceTitles(document.getElementsByTagName('h1'));
  replaceTitles(document.getElementsByTagName('h2'));
  replaceTitles(document.getElementsByTagName('a'));
}

function replaceTitles(tags)
{
  for (var i = 0; i < tags.length; i++)
  {
    if (tags[i].id)
    {
      var image = document.createElement('img');
      image.className = tags[i].className;
      image.src = 'images/' + tags[i].id + '.png';;
      image.alt = tags[i].firstChild.nodeValue;
      image.title = tags[i].firstChild.nodeValue;
      tags[i].replaceChild(image,tags[i].firstChild);
    }
  }
}