var i = 0;

function trocarBanner() {

	if (banners.length > 0) {

		if (i >= banners.length) {
			i = 0;
		}

		document.getElementById("bannerEspecialLink").href = banners[i].url;
		document.getElementById("bannerEspecial").src = "/img/banner/" + banners[i].imagem;
		document.getElementById("bannerEspecial").alt = banners[i].alt;
		i++;

	}

}

var tempoDoIntervalo = 4000;

var intervalo = setInterval("trocarBanner()", tempoDoIntervalo);