主要文件
注意： jQuery文件,务必在bootstrap.min.js 之前引入
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Bootstrap所需文件引入</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1">
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css">
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap-theme.min.css">
<script src="http://cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script>
<script src="http://cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</head>默认的点击下拉展开变为悬浮展开
.nav> li:hover .dropdown-menu {display: block;}带菜单栏的Bootstrap
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Bootstrap所需文件引入</title>
<meta http-equiv="X-UA-Compatible" content="IE=edge,chrome=1">
<meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1">
<!-- Bootstrap 核心 CSS 文件 -->
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css">
<!-- 可选的Bootstrap主题文件（一般不用引入） -->
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap-theme.min.css">
<!-- jQuery文件,务必在bootstrap.min.js 之前引入 -->
<script src="http://cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script>
<!-- Bootstrap 核心 JavaScript 文件 -->
<script src="http://cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
</head>
<style>
<!--默认的点击下拉展开变为悬浮展开-->
.nav> li:hover .dropdown-menu {display: block;}
</style>
<body>
<nav class="navbar navbar-default" role="navigation">
<div class="container-fluid">
<div class="navbar-header">
<!--手机端展开栏-->
<button type="button" class="navbar-toggle" data-toggle="collapse" data-target="#example-navbar-collapse">
<ul>
<li class="sr-only"></li>
<li class="icon-bar"></li>
<li class="icon-bar"></li>
<li class="icon-bar"></li>
</ul>
</button>
<a class="navbar-brand" href="#">Bootstrap</a>
</div>
<div class="collapse navbar-collapse" id="example-navbar-collapse">
<ul class="nav navbar-nav">
<li class="active"><a href="#">第一栏</a></li>
<li><a href="#">第二栏</a></li>
<li class="dropdown">
<a href="#" data-toggle="dropdown">
下拉栏 <b class="caret"></b>
</a>
<ul class="dropdown-menu">
<li><a href="#">下拉一</a></li>
<li><a href="#">下拉二</a></li>
<li><a href="#">下拉三</a></li>
<li class="divider"></li>
<li><a href="#">与上面隔开的栏</a></li>
<li class="divider"></li>
<li><a href="#">隔开栏是class="divider"</a></li>
</ul>
</li>
</ul>
</div>
</div>
</nav>
</body>
</html>