var img1 = new Image(35,34);
var img2 = new Image(35,34);
img1.src = "images/btn1.gif";
img2.src = "images/btn2.gif";

function highlight(imgName) {
	var img = document.images[imgName];
	img.src = img2.src;
}

function normal(imgName) {
	var img = document.images[imgName];
	img.src = img1.src;
}