function smartRollover() {  
		if(document.getElementsByTagName) {  
		var images = document.getElementsByTagName("img");  
		for(var i=0; i < images.length; i++) {  
			if(images[i].getAttribute("src").match("_of.")){  
				images[i].onmouseover = function(){  
				this.setAttribute("src", this.getAttribute("src").replace("_of.", "_on."));  
				}
				images[i].onmouseout = function() { 
				this.setAttribute("src", this.getAttribute("src").replace("_on.", "_of."));  
				}
			}  
		}  
}  
}

if(window.addEventListener){  
	window.addEventListener("load", smartRollover, false);  
}  
else if(window.attachEvent){  
	window.attachEvent("onload", smartRollover);  
}