var _preloaded = null;
function preload(preload) {
	_preloaded = [];
	for(var i = 0, l = preload.length; i < l; i++) {
		_preloaded[i] = document.createElement("img");
		_preloaded[i].src = preload[i];
	}
}

function swapImg(evt, newImg, imgId) {
	var dst = imgId ? document.getElementById(imgId) : (evt.srcElement || evt.target);
	dst.src = typeof(newImg) == "number" ? _preloaded[newImg].src : newImg;
}