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

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