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);
}