function prepare() {
	
	var navs = document.getElementById("main_navigation").getElementsByTagName("img");
	var preload = new Array;
	
	for (var x=0; x<navs.length; x++) {
		if (navs[x].src.indexOf("_hl_") == -1)
			navs[x].altImg = navs[x].src.replace("_", "_hl_");

		navs[x].onmouseover = navs[x].onmouseout = function() {
			if (!this.altImg) return;
			
			var oldSrc = this.src;
			this.src = this.altImg;
			this.altImg = oldSrc;
		}
		
		preload[x] = new Image;
		preload[x].src = navs[x].altImg;
	}
}

window.onload = prepare;