// ロールオーバー
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);
}