学习网址：http://www.bootcss.com/
下载网址：http://v3.bootcss.com/
下载后一共三个文件夹 css js fonts
引入的文件
<link rel="stylesheet" href="//cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css"/><script src="//cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script><script src="//cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
<!-- 新 Bootstrap 核心 CSS 文件 -->
<link rel="stylesheet" href="//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="//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="//cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script>
<!-- 最新的 Bootstrap 核心 JavaScript 文件 -->
<script src="//cdn.bootcss.com/bootstrap/3.3.5/js/bootstrap.min.js"></script>
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<!-- 上述3个meta标签*必须*放在最前面，任何其他内容都*必须*跟随其后！ -->
<title>Bootstrap 101 Template</title> <!-- Bootstrap -->
<link href="css/bootstrap.min.css" rel="stylesheet"> <!-- HTML5 shim and Respond.js for IE8 support of HTML5 elements and media queries -->
<!-- WARNING: Respond.js doesn't work if you view the page via file:// -->
<!--[if lt IE 9]>
<script src="//cdn.bootcss.com/html5shiv/3.7.2/html5shiv.min.js"></script>
<script src="//cdn.bootcss.com/respond.js/1.4.2/respond.min.js"></script>
<![endif]-->
</head>
<body>
<h1>你好，世界！</h1> <!-- jQuery (necessary for Bootstrap's JavaScript plugins) -->
<script src="//cdn.bootcss.com/jquery/1.11.3/jquery.min.js"></script>
<!-- Include all compiled plugins (below), or include individual files as needed -->
<script src="js/bootstrap.min.js"></script>
</body>
</html>