// Preload image - incase they are large images.
if(document.images){
  var main = new Image(); main.src = "ngm_images/link pages/programming/2up.jpg";
  var img1 = new Image(); img1.src = "ngm_images/link pages/programming/cross.jpg";
  var img2 = new Image(); img2.src = "ngm_images/link pages/programming/dome.jpg";
}

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

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