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/portada/blanco.gif","images/banderas/ban_esp1.gif","images/banderas/ban_esp2.gif","images/banderas/ban_eng1.gif","images/banderas/ban_eng2.gif","images/banderas/ban_ger1.gif","images/banderas/ban_ger2.gif","images/banderas/ban_fra1.gif","images/banderas/ban_fra2.gif","images/portada/inicio_1x1.jpg","images/portada/inicio_1x2.jpg","images/portada/inicio_1x3.jpg","images/portada/inicio_2x1.jpg","images/portada/inicio_2x2.jpg","images/portada/inicio_2x3.jpg","images/portada/inicio_3x1.jpg","images/portada/inicio_3x2.jpg","images/portada/inicio_3x3.jpg","images/portada/inicio_4x1.jpg","images/portada/inicio_4x2.jpg","images/portada/inicio_4x3.jpg","images/portada/frase_esp.jpg","images/portada/frase_eng.jpg","images/portada/frase_ger.jpg","images/portada/frase_fra.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,nombre1,index1){
		if ((browserIE)||(browserNS2)){
							
			document.images[nombre].src = lista_imagenes[parseInt(index)].src;			
			document.images[nombre1].src = lista_imagenes[parseInt(index1)].src;
		}	
		else if (browserNS1){	
		
			document.layers["portada"].document.images[nombre].src = lista_imagenes[parseInt(index)].src;			
			document.layers["portada"].document.images[nombre1].src = lista_imagenes[parseInt(index1)].src;
		}
}