Bootstrap系列 -- 40. 导航条二级菜单

<div class="navbar navbar-default" role="navigation">
  　<div class="navbar-header">
  　    <a href="##" class="navbar-brand">导航条</a>
  　</div>
    <ul class="nav navbar-nav">
         <li class="active"><a href="##">网站首页</a></li>
        <li class="dropdown">
          <a href="##" data-toggle="dropdown" class="dropdown-toggle">系列教程<span class="caret"></span></a>
          <ul class="dropdown-menu">
            <li><a href="##">CSS3</a></li>
            <li><a href="##">JavaScript</a></li>
            <li class="disabled"><a href="##">PHP</a></li>
          </ul>
       </li>
       <li><a href="##">名师介绍</a></li>
       <li><a href="##">成功案例</a></li>
       <li><a href="##">关于我们</a></li>
    </ul>
</div>