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/quienes.gif","images/menu/quienesBis.gif","images/menu/cursos.gif","images/menu/cursosBis.gif","images/menu/localizacion.gif","images/menu/localizacionBis.gif","images/menu/equipamiento.gif","images/menu/equipamientoBis.gif","images/menu/empleo.gif","images/menu/empleoBis.gif","images/menu/partners.gif","images/menu/partnersBis.gif","images/menu/contacto.gif","images/menu/contactoBis.gif","images/menu/aulas.gif","images/menu/aulasBis.gif");
 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["ms"].document.images[nombre].src = lista_imagenes[parseInt(index)].src;
       }
}