function imgRollOver(id) {
	var el = document.getElementById('ss'+id);
	var src =  el.src.replace('.png','_ro.png');
	el.src = src;
}

function imgRollOut(id) {
	var el = document.getElementById('ss'+id);
	var src = el.src.replace('_ro.png','.png');
	el.src = src;
}

window.onload = function() {
	var imgs = document.getElementsByTagName("img");
	for (var i=0; i < imgs.length; i++) {
		if (imgs[i].id.match("ss1")) {
			var _img = new Image();
			var src = imgs[i].src.replace('.png','_ro.png');
			_img.src = src;
		}
	};
}

var preloaded = [];
function preload(ar) {
	for (var i=0; i < ar.length; i++) {
		var img = new Image();
		img.src = ar[i];
		preloaded.push(img);
	};
}