one-level drop-down menu

HTML

<div class="list-wrapper">
    <ul class="items">
        <li>stackoverflow</li>
        <li>superuser</li>
        <li>serverfault</li>
    </ul>
</div>
<p>Stack Exchange is a fast-growing network of 76 question and answer sites on diverse topics from software programming to cooking to photography and gaming.</p>

CSS

.list-wrapper,
.items {
   display: inline-block;
}

.list-wrapper {
    position: relative;
    background-color: blue;
    height: 1em;
}

.items {
    position: absolute;
    background-color: red;
}

.items > li:first-child ~ li {
    display: none;
}

.items:focus > li:first-child ~ li {
    display: block;
}

JavaScript

/* one-level drop-down menu */