var current_image;

function next_image()
{
  current_image.fade();
  current_image = current_image.next() || $('main').down('.right').down();
  current_image.appear();
}

document.observe("dom:loaded", function(){
  if($('main'))
  {
    current_image = $('main').down('.right').down();
    new PeriodicalExecuter(next_image, 5);
  }
});