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 style='width:550px;padding-left:40%;padding-top:100px;float:left;'><img src='loading.gif'><br></div><span style='width:550px;padding-top:205px;padding-left:39%; color:#999999;font-size:7pt; font-family:Verdana, Geneva, sans-serif; '>Aguarde</span>";   
}   

  
return url;   
}   
  
function mudancaEstado(){   
if (xmlRequest.readyState == 4){   
document.getElementById("conteudo_mostrar").innerHTML = xmlRequest.responseText;   
}   
}