// pre-carga de imagenes
function preloadImg() {
	var doc = document;
	if(doc.images) {
		if(!doc.preLoaded) { doc.preLoaded = new Array(); }
		var aUrlImages = preloadImg.arguments;
		for(var x = 0; x < aUrlImages.length; x++) {
			tmpImg = new Image;
			tmpImg.src = aUrlImages[x];
		}
	}
}

// cambia las imagenes
function swapImg(img, name) {
	if(name) {
		prevImg = img.src;
		img.src = 'images/'+name;
	} else {
		img.src = prevImg;
	}
}