$(document).ready(function() {
    jQuery.preloadImages = function() {
        for(var i = 0; i<arguments.length; i++) {
            jQuery("<img>").attr("src", arguments[i]);
        }
    }
    
    $(".rollover").hover(
     function()  {
      this.src = this.src.replace("_off","_on");
     },
     function() {
      this.src = this.src.replace("_on","_off");
     }
    );
    
        // Navigation rollovers
    $("#nav a img").mouseover(function(){
        this.src = this.src.replace("_off","_on");
    });
    
        // Navigation rollovers
    $("#nav a img").mouseout(function(){
      this.src = this.src.replace("_on","_off");
    });    
    
 });