function smartRollover() {
	if(document.getElementsByTagName) {
		var images = document.getElementsByTagName("img");

		for(var i=0; i < images.length; i++) {
			if(images[i].getAttribute("src").match("btn_"))
			{
				if(images[i].getAttribute("src").match(/gif$/))
				{
					images[i].onmouseover = function() {
						if(!this.getAttribute("src").match(/_on\.gif$/))
						{
							this.setAttribute("src", this.getAttribute("src").replace(".gif", "_on.gif"));
						}
					}
					images[i].onmouseout = function() {
						this.setAttribute("src", this.getAttribute("src").replace("_on.gif", ".gif"));
					}
				}
				
				if(images[i].getAttribute("src").match(/jpg$/))
				{
					images[i].onmouseover = function() {
						if(!this.getAttribute("src").match(/_on\.jpg$/))
						{
							this.setAttribute("src", this.getAttribute("src").replace(".jpg", "_on.jpg"));
						}
					}
					images[i].onmouseout = function() {
						this.setAttribute("src", this.getAttribute("src").replace("_on.jpg", ".jpg"));
					}
				}
			}
		}
	}
}

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