var aryImages = new Array(2);

  aryImages[00] = "img/main/bothy-01.jpg";
  aryImages[01] = "img/main/bothy-02.jpg";
  aryImages[02] = "img/main/bothy-03.jpg";
  aryImages[03] = "img/main/bothy-04.jpg";
  aryImages[04] = "img/main/bothy-05.jpg";

  for (i=0; i < aryImages.length; i++) {
    var preload = new Image();
    preload.src = aryImages[i];
  }

  function swap(imgIndex) {
    document['imgMain'].src = aryImages[imgIndex];
  }