benefit
There is no need to download the bootstrap document in advance and call it again, you can use it directly after quoting
code show as below:
<!--在线引入bootstrap -->
<link rel="stylesheet" href="http://cdn.bootcss.com/bootstrap/3.3.0/css/bootstrap.min.css">
<script src="http://cdn.bootcss.com/bootstrap/3.3.0/js/bootstrap.min.js"></script>
Place: in <head> </ head>
