【border_bottom】
<!DOCTYPE html>
<html>
<head>
<style type='text/css'>
ul {
border-bottom: 1px solid #f00;
}
li {
display: inline-block;
padding: 0.2em 0.5em;
border: 1px solid #000;
border-bottom-width: 0;
margin: 0 0 -1px 1em;
}
</style>
</head>
<body>
<nav>
<ul>
<li>box one</li>
<li>box two</li>
<li>box three</li>
</ul>
</nav>
</body>
</html>
