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