function muestra_submenu(id) {
  if (id==1) { 
    document.getElementById('submenu1').style.display = ''; 
    document.getElementById('submenu2').style.display = 'none';
  } else { 
    document.getElementById('submenu2').style.display = ''; 
    document.getElementById('submenu1').style.display = 'none';	  
  }
  return true;
}

function nuevoAjax(){ 
  var req;
  if (window.XMLHttpRequest) {
    req = new XMLHttpRequest();
  } else {
    req = new ActiveXObject("Microsoft.XMLHTTP");
  }  
  return req;
}