var ie = (document.all) ? true : false;
var moz = (document.getElementById && !document.all) ? true : false;

function swapImage(imageNumber)
{
  if (moz)
  {
    document.getElementById('photograph').src = 'image_bin/gallery/large/' + imageNumber +'.jpg';
  }
  if (ie)
  {
    document.all.photograph.src = 'image_bin/gallery/large/' + imageNumber +'.jpg';
  }
}