官网： www.bootcss.com
bootstrap 响应式的： 根据浏览器的放大缩小，内容也跟着放大缩小
需要添加：html的head中添加meta name="viewport" content="width=device-width, initial-scale=1"
@media媒体查询
一套页面适用于pc,手机，平板设备
但需要写多套css
准备工作3点：
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title></title>
<!--使用@media 必须做以下操作-->
<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />
<!-- 去掉注释
[if lt IE 9]>
<script src="https://oss.maxcdn.com/libs/html5shiv/3.7.0/html5shiv.js"></script>
<script scr="https://oss.maxcdn.com/libs/respond.js/1.3.0/respond.min.js"></script>
<![endif]
-->
<meta http-equiv="X-UA-Compatible" content="IE=Edge, chrome=1">
<style type="text/css">
*{padding: 0;margin: 0;}
@media screen and (max-width:500px ) {
.box{
width: 200px;
height: 300px;
background: yellow;
}
}
/*300px ~600px之间显示的样式*/
@media screen and (min-width: 500px) and (max-width: 800px) {
.box{
width: 200px;
height: 300px;
background: red;
}
}
@media screen and (min-width:800px ) {
.box{
width: 200px;
height: 300px;
background: green;
}
}
</style>
</head>
<body>
<div class="box">
</div>
</body>
</html>
原文：https://www.cnblogs.com/beallaliu/p/9718828.html