 <p>Sure, just transition <code>border</code> or <code>border-width</code> on the <code>a</code> element:</p> <pre><code>nav a { /* -moz-, -o-, -webkit- prefixes omitted for brevity */ transition: border-width 0.1s ease-in-out; border-bottom: 1px solid #AADA4B; } </code></pre>