var aryImages = new Array(2);

  aryImages[00] = "img/main/longshot-01.jpg";
  aryImages[01] = "img/main/distillery-01.jpg";
  aryImages[02] = "img/main/forest-02.jpg";
  aryImages[03] = "img/main/cairngorms-04.jpg";
  aryImages[04] = "img/main/spey-valley-01.jpg";

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

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