Event.observe(window, 'load', function(){
  // this array consists of the id attributes of the divs we wish to alternate between
  var divs_to_fade = new Array($('slide-1'), $('slide-2'), $('slide-3'), $('slide-4'), $('slide-5'));

  // the starting index in the above array.  It should be set to the value of the div which doesn't have the CSS Display property set to "none"
  var i = 0;

  // the number of milliseconds between swaps.  Default is five seconds.
  var wait = 5000;

  // the function that performs the fade
  function swapFade() {
    Effect.Fade(divs_to_fade[i], { duration:1, from:1.0, to:0.0 });
    i++;
    if (i == 5) i = 0;
    Effect.Appear(divs_to_fade[i], { duration:1, from:0.0, to:1.0 });
  }

  setInterval(swapFade,wait);
});