// Preload image - incase they are large images.
if(document.images){
  var main = new Image(); main.src = "main.gif";
  var img1 = new Image(); img1.src = "1.gif";
  var img2 = new Image(); img2.src = "2.gif";
  var img3 = new Image(); img3.src = "3.gif";
  var img4 = new Image(); img4.src = "4.gif";
  var img5 = new Image(); img5.src = "5.gif";
  var img6 = new Image(); img6.src = "6.gif";
}

function change(imageName){
  if(document.images){ document['main'].src = eval(imageName + ".src"); }
}

function changeBack(){
  if(document.images){ document['main'].src = main.src; }
}