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.", "_over."));  
        }  
        images[i].onmouseout = function() {  
          this.setAttribute("src", this.getAttribute("src").replace("_over.", "_off."));  
        }
      }
    }  
  } 
}  
if(window.addEventListener) {  
    window.addEventListener("load", smartRollover, false);  
}  
else if(window.attachEvent) {  
    window.attachEvent("onload", smartRollover);  
}