function addHovers() {
    var images = $$('img.rollover');
    
    images.each(function(image) {
       image.observe('mouseover', function(e) { 

        image.src = $F(image.id + "_rollover");
       });
       
       image.observe('mouseout', function(e) { 
        image.src = $F(image.id + "_rollout");
       });
      
    });
};
  
Event.observe(window, 'load', function() {
  addHovers();
});