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);
}
/*
function smartOver() {
smartRollover('menu'); //ロールオーバーを適用させたい箇所のIDを指定
smartRollover('test');
}
function smartRollover(idName) {
if(document.getElementsByTagName) {
var images = document.getElementById(idName).getElementsByTagName("img");
for(var i=0; i < images.length; i++) {

if(images[i].getAttribute("src").match(/_no\./))
{
fileName = new Array(images[i].getAttribute("src").replace("_no.", "_ov."));
preImages = new Array();
for (j=0; j<fileName.length; j++)
{
preImages[j] = new Image();
preImages[j].src = fileName[j]; //「_on」の画像をプリロード
}

images[i].onmouseover = function() {
this.setAttribute("src", this.getAttribute("src").replace("_no.", "_ov.")); //マウスオーバーで_off→_on
}
images[i].onmouseout = function() {
this.setAttribute("src", this.getAttribute("src").replace("_ov.", "_no.")); //マウスが離れたら_on→_off
}
}
}
}
}
if(window.addEventListener) {
window.addEventListener("load", smartOver, false); //実行
}
else if(window.attachEvent) {
window.attachEvent("onload", smartOver);
}
else{
window.onload = smartOver;
}
*/