function smartRollover() {  
  if(document.getElementsByTagName) {  
    var images = document.getElementsByTagName("img");  
    var preImages = new Array();  
      for(var i=0; i < images.length; i++) {  
        if(images[i].getAttribute("src").match("_off.")) {  
        var preImage = new Image();  
        preImage.src =  
        images[i].getAttribute("src").replace("_off.", "_on.");  
        preImages.push(preImage);  
        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);  
}  // JavaScript Document