function rollOver() {
	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."));	}
			}
		}
	}
}


/* 下記処理は、ブラウザがすべてを読み込んでから実行 */
if(window.addEventListener) {
/* IE以外用 */
window.addEventListener("load", rollOver, false);
}
else if(window.attachEvent) {
/* IE用 */
window.attachEvent("onload", rollOver);
}
else{
/* 古い記述 */
window.onload = rollOver;
}