// si es explorer
// CHRONE Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US) AppleWebKit/532.5 (KHTML, like Gecko) Chrome/4.0.249.89 Safari/532.5

if (strstr($_SERVER['HTTP_USER_AGENT'],"Mozilla/4.0")){ // SI ES IE
	if ((!strstr($_SERVER['HTTP_USER_AGENT'],"MSIE 7.0")) && (!strstr($_SERVER['HTTP_USER_AGENT'],"MSIE 8.0"))){ // si no estoy en 7 u 8
		header("Location: update.html");
	} else {
		header("Location: index.html");	
	}	
} else {
	header("Location: index.html");
}
?>