<div class="navbar navbar-inverse navbar-fixed-top" role="navigation">
<ul class="nav navbar-nav">
<li class="navbar-header"><a href="#" class="navbar-brand"
>某网站管理系统</a></li>
<li class="active"><a href="##">首页</a></li>
<li class="dropdown">
<a href="#" data-toggle="dropdown" class="dropdown-toggle">
功能<span class="caret"></span>
</a>
<ul class="dropdown-menu">
<li><a href="#">菜单一</a></li>
<li><a href="#">菜单二</a></li>
<li><a href="#">菜单三</a></li>
</ul>
</li>
<li><a href="##">帮助</a></li>
</ul>
</div>
是不是你jquery库版本不够,看一下页面控制台
明白了,src 手误,打成SCR了
<scrpit scr="http://cdn.bootcss.com/jquery/1.11.1/jquery.min.js"></scrpit>
<scrpit scr="http://cdn.bootcss.com/bootstrap/3.2.0/js/bootstrap.min.js"></scrpit>