SO Q6

HTML

<nav>
    <ul>
        <li><a href="#">First</a></li>
        <li class="subMenu"><a href="#">Second</a>
            <ul>
                <li><a href="#">First Child</a></li>
            </ul>
        </li>
        <li><a href="#">Third</a></li>
    </ul>
</nav>

CSS

nav {
    width: 50%;
    margin: 0 auto;
}

nav a {
    display: block;
    text-decoration: none;
    color: #2b2b2b;
}

nav a:hover {
    color: #fff;
}

nav ul {
    list-style-type: none;
    margin: 0;
    padding: 0;
}

nav ul li {
    float: left;
    width: 33%;
    background: #ff7200;
    text-align: center;
}

nav ul li:hover {
    background: #2b2b2b;
}

nav ul li ul {
    display: none;
    height: 100px;
    background: #ff7200;
}

JavaScript

$('.subMenu').on('click', function() {
    $('.subMenu ul').slideToggle(500);
});