function navi() {  
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", navi, false);  
}  
else if(window.attachEvent) {  
    window.attachEvent("onload", navi);  
}