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.")) 
if(images[i].getAttribute("src") != null || 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);  
}