Another option with pure CSS would be something like this:
nav { margin: 0px auto; width: 100%; height: 50px; background-color: white; float: left; padding: 10px; border: 2px solid red; position: relative; z-index: 10; } nav:after { background-color: grey; content: ''; display: block; position: absolute; top: 10px; left: 10px; right: 10px; bottom: 10px; z-index: -1; }
<nav>Some text or anything</nav>
Demo here