<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Hello World</title>
<link href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css" rel="stylesheet">
<link rel="stylesheet" href="css/page.css">
<!--[if lt IE 9]>
<script src="https://oss.maxcdn.com/html5shiv/3.7.2/html5shiv.min.js"></script>
<script src="https://oss.maxcdn.com/respond/1.4.2/respond.min.js"></script>
<![endif]-->
</head>
<body>
<nav class="navbar navbar-default" role="navigation">
<div>
<div>
<button type="button" class="nva-toggle collapsed" data-toggle="collapse" data-target="#bs-example-navbar-collapse-1" aria-expanded="false">
<span>Toggle navigation</span>
<span></span>
<span></span>
</button>
<a href="#">某管理系统</a>
</div>
<div class="collapse navbar-collapse" id="bs-example-navbar-collapse-1">
<ul class="nav navbar-nav">
<li><a href="#">首页</a></li>
<li>
<a href="#" data-togglr="dropdown">功能<span></span></a>
<ul role="menu">
<li><a href="#">业务功能</a></li>
<li><a href="#">信息建立</a></li>
<li><a href="#">信息查询</a></li>
<li><a href="#">信息管理</a></li>
<li></li>
<li><a href="#">系统设置</a></li>
<li><a href="#">设置</a></li>
</ul>
</div>
</li>
</ul>
<form class="navbar-form navbar-right" role="search">
<div>
<input type="text" class="form=control" placeholder="username">
<input type="password" placeholder="password">
</div>
<button type="submit" class="btn btn-default btn-info">登录</button>
</form>
</div>
</nav>
<script src='http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js'></script>
<script src='http://cdn.bootcss.com/bootstrap/3.2.0/js/bootstrap.min.js'></script>
</body>
</html>
<a href="#" data-togglr="dropdown">功能<span></span></a>
这里的data-togglr改成data-toggle 写错了哦，同学。
写错字了