在<head></head>中添加
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewpport" content="width=device-width,initial-scale=1">
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.4/css/bootstrap.min.css">
搞定