function menuSwitch(backgroundImage, backgroundPosition) {
    if (
        typeof backgroundImage != "undefined" 
        && 
        typeof backgroundPosition != "undefined"
    ) {
        document.getElementById('introimage').style.background = 'url(/home-menu/' + backgroundImage + ') no-repeat ' + backgroundPosition;
    }
    else {
        document.getElementById('introimage').style.background = 'url(/home-menu/default.jpg) no-repeat bottom right';
    }
}