function abrirPag(valor){
	var url = valor;
	xmlRequest.open("GET",url,true);
	xmlRequest.onreadystatechange = mudancaEstado;
	xmlRequest.send(null);
	if (xmlRequest.readyState == 1) {
		document.getElementById("conteudo_mostrar").innerHTML = "<div align='center'><img src='fatias/img_carregando.gif' /></div>";
	}
	return url;
}
function mudancaEstado(){
	if (xmlRequest.readyState == 4){
		document.getElementById("conteudo_mostrar").innerHTML = xmlRequest.responseText;
	}
}