MagicLine is a jQuery plugin that append a div to your menu, following the user's hover.
All you need is a simple html structure :
<ul>
<li id="yourNavbar" class="active"><a href="#">First</a></li>
<li><a href="#">Second</a></li>
<li><a href="#">Third</a></li>
<li><a href="#">Fourth</a></li>
<li><a href="#">Fifth</a></li>
</ul>
Add this line to your css
#magic-line{ width: 100px; height: 6px; position: absolute; bottom: 0px; left: 0; background: #000;}
Then you need a recent version of jQuery and the following initialization :
<script src="/magic-line.js'"></script>
<script>
$(document).ready(function() {
$('#yourNavbar').magicLine();
});
</script>