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","galeria").innerHTML = "";  

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