(function () {
	if (window.addEventListener) {
		window.addEventListener("load", setupRollovers, false);
	} else if (window.attachEvent) {
		window.attachEvent("onload", setupRollovers);
	}
	
	function setupRollovers () {
		if (!document.getElementById || !document.getElementsByTagName) {
			return false;
		}
		if (!document.getElementById("header")) {
			return false;
		}
		var header = document.getElementById("header");
		var links = header.getElementsByTagName("img");
		var classRegExp = /(^|\s)nav_button(\s|$)/;
		for (var i = 0; i < links.length; i++) {
			if (classRegExp.test(links[i].className)) {
				links[i].onmouseover = function () {
					this.src = "images/" + this.id + ".gif";
				}
				links[i].onmouseout = function () {
					var id = this.id;
					this.src = "images/" + id.substring(0, id.length-3) + ".gif";
				}
				var id = links[i].id;
				(new Image()).src = "images/" + id + ".gif";
			}
		}
	}
})();