if (document.images) {            // Active Images
            img11on = new Image();      
            img11on.src = "imagenes/menu_mapaweb_on.gif"; 
            img12on = new Image();      
            img12on.src = "imagenes/menu_contactar_on.gif"; 
            img13on = new Image();      
            img13on.src = "imagenes/menu_localizacion_on.gif"; 
                                                
            img11off = new Image();      
            img11off.src = "imagenes/menu_mapaweb_off.gif"; 
            img12off = new Image();      
            img12off.src = "imagenes/menu_contactar_off.gif"; 
            img13off = new Image();      
            img13off.src = "imagenes/menu_localizacion_off.gif"; 
        }

// Function to 'activate' images.
function imgOn(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "on.src");
        }
}

// Function to 'deactivate' images.
function imgOff(imgName) {
        if (document.images) {
            document[imgName].src = eval(imgName + "off.src");
        }
}