不显示下拉框
我是在dreamweaver上写的代码，下拉按钮菜单可以显示，但是下拉框显示不出来，查看代码也没有错误，不明白为什么
<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.1.1/css/bootstrap.min.css">
<script src="http://libs.baidu.com/jquery/1.9.0/jquery.js"></script>
<script src="//maxcdn.bootstrapcdn.com/bootstrap/3.2.0/js/bootstrap.min.js"></script>
</head>
<body style="padding:50px 50px">
<div class="dropdown">
<button class="btn btn-default dropdown-toggle" type="button" id="dropdownMenu1" data-toggle="dropdown">
下拉菜单
<span class="caret"></span>
</button>
<ul class="dropdown-menu" role="menu" aria-labelledby="dropdownMenu1">
<li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li>
<li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li>
<li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li>
<li role="presentation"><a role="menuitem" tabindex="-1" href="#">下拉菜单项</a></li>
</ul>
</div>
</body>
