footer {
    background: #333;
    color: #fff;
    text-align: center;
    position: fixed;
    bottom: 0;
    width: 100%;
    height: 40px;
}

@media (max-width: 480px) {
    footer {
        background: #333;
        color: #fff;
        text-align: center;
        position: fixed;
        bottom: 0;
        max-width: 100%;
        height: 40px;
        font-size: 12px;
    }
}