function initRollOverImages() {  
     var image_cache = new Object();  
     $(".rollover a img").not("[@src*='_on.']").each(function(i) {  
         var imgsrc = this.src;  
          var dot = this.src.lastIndexOf('.');  
          var imgsrc_on = this.src.substr(0, dot) + '_on' + this.src.substr(dot, 4);  
         image_cache[this.src] = new Image();  
         image_cache[this.src].src = imgsrc_on;  
         $(this).hover(  
             function() { this.src = imgsrc_on; },  
             function() { this.src = imgsrc; }  
         );  
     });  
}  
$(document).ready(initRollOverImages);