function smartRollover() {  
    if(document.getElementsByTagName) {  
        var images = document.getElementsByTagName("img");  
         for(var i=0; i < images.length; i++) {  
            if(images[i].getAttribute("src").match("_off."))  
           {  
                images[i].onmouseover = function() {  
                   this.setAttribute("src", this.getAttribute("src").replace("_off.", "_on."));  
                }  
                images[i].onmouseout = function() {  
                   this.setAttribute("src", this.getAttribute("src").replace("_on.", "_off."));  
                }  
             }  
         }  
     }  
 }  
if(window.addEventListener) {  
     window.addEventListener("load", smartRollover, false);  
 }  
 else if(window.attachEvent) {  
     window.attachEvent("onload", smartRollover);  
}