function preloadImages() {
  if (!document.preload)
    document.preload = new Array();
  var i, j = document.preload.length, a = preloadImages.arguments;
  for (i = 0; i < a.length; i++) {
    document.preload[j] = new Image;
    document.preload[j++].src = a[i];
  }
}

function changeImage(name,file) {
  var d = document.getElementById(name);
  d.src = file;
}