代码如下：
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=GB18030">
<title>学生试题库管理信息系统</title>
<link href="http://cdn.bootcss.com/bootstrap/3.3.4/css/bootstrap.css" rel="stylesheet">
<script src="http://cdn.bootcss.com/jquery/1.10.2/jquery.min.js"></script>
<script src="http://cdn.bootcss.com/bootstrap/3.3.4/js/bootstrap.min.js"></script>
<style>
#subMenu {
display: none;
position: fixed;
top: 55px;
left: 10px;
}
</style>
<script>
function hiddenSubMenu() {
var m = document.getElementById("subMenu");
m.style.display = "none";
}
</script>
</head>
<body background="2.jpg">
<br>
<table>
<tr><td>
<nav class="navbar navbar-default" role="navigation">
<div class="navbar-header">
<a class="navbar-brand" href="#" data-toggle="dropdown">用户管理</a>
<ul class="dropdown-menu">
<li><a href="register.jsp">新用户注册</a></li>
<li><a href="#">修改密码</a></li>
<li><a href="#">用户注销</a></li>
<li class="divider"></li>
<li><a href="#">文件备份</a></li>
<li><a href="#">文件恢复</a></li>
</ul>
</div>
</nav></td>
<td><nav class="navbar navbar-default" role="navigation">
<div class="navbar-header">
<a class="navbar-brand" href="#" data-toggle="dropdown">文件管理</a>
</div>
</nav></td>
<td><nav class="navbar navbar-default" role="navigation">
<div class="navbar-header">
<a class="navbar-brand" href="#" data-toggle="dropdown">信息查询</a>
</div>
</nav></td>
<td><nav class="navbar navbar-default" role="navigation">
<div class="navbar-header">
<a class="navbar-brand" href="#" data-toggle="dropdown">报表输出</a>
</div>
</nav></td>
<td><nav class="navbar navbar-default" role="navigation">
<div class="navbar-header">
<a class="navbar-brand" href="#" data-toggle="dropdown">退出系统</a>
</div>
</nav></td></tr>
</body>
</html>