var nav = navigator
browserIE = ((nav.appName == "Microsoft Internet Explorer") && (parseInt(nav.appVersion) >= 4 ))
browserNS1 = ((nav.appName == "Netscape") && (parseInt(nav.appVersion) < 5 ) ) // Netscape < 4.7
browserNS2 = ((nav.appName == "Netscape") && (parseInt(nav.appVersion) >= 5 ) )// Netscape >= 6

// Precarga de imágenes ----------------------------------------
var i;
var imagenes = new Array("images/menu/quiensoy.jpg","images/menu/quiensoyBis.jpg","images/menu/mislibros.jpg","images/menu/mislibrosBis.jpg","images/menu/grafologia.jpg","images/menu/grafologiaBis.jpg","images/menu/suenos.jpg","images/menu/suenosBis.jpg","images/menu/articulos.jpg","images/menu/articulosBis.jpg","images/menu/paranormal.jpg","images/menu/paranormalBis.jpg");
var lista_imagenes = new Array();
function cargarimagenes(){
for(i in imagenes){
lista_imagenes[i] = new Image();
lista_imagenes[i].src = imagenes[i];
}
}

function cambio(nombre,index){
  if ((browserIE)||(browserNS2))
  {
      document.images[nombre].src = lista_imagenes[parseInt(index)].src;
  }
  else if (browserNS1)
  {
      document.layers["menu"].document.images[nombre].src = lista_imagenes[parseInt(index)].src;
  }
}