The following code shows how to place stack navbar under inner navbar.
<!DOCTYPE html>
<html>
<head>
<script type='text/javascript'
src='http://code.jquery.com/jquery-1.8.3.js'></script>
<script type='text/javascript'
src="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.1.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" type="text/css"
href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.1.0/css/bootstrap.min.css">
<!--from w ww .j a v a2s .c o m-->
</head>
<body style='margin:30px'>
<div class="navbar">
<div class="navbar-inner">
<a class="brand" href="#">Title</a>
<ul class="nav">
<li class="active"><a href="#">Home</a></li>
<li><a href="#">Link</a></li>
<li><a href="#">Link</a></li>
</ul>
</div>
</li>
</ul>
</div>
</div>
<div class="bs-docs-example">
<ul class="nav nav-tabs nav-stacked">
<li class="active"><a href="#">Home</a></li>
<li><a href="#">Profile</a></li>
<li><a href="#">Messages</a></li>
</ul>
</div>
</body>
</html>