function topes(){
	//gotta set the number of available banners
	$hasta = 5;
	$vieja = $("#imgBannerPrincipal").attr("src");
	var $i;
	var $key;
	var $imagen;
	var $arr = new Array();
	for ($i=1;$i<=$hasta;$i++){
		$nueva = "imagenes/topes/banner"+$i+".jpg";
		if($nueva != $vieja){
			$arr.push($nueva);
		} 	
	}
	$key = Math.floor(Math.random() * $arr.length);
	$imagen = $arr[$key];
	$("#imgBannerPrincipal").attr("src",$imagen);
}