标准代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1.0,maximum-scale=1.0,minimum-scale=1.0,user-scalable=no">
<title>flex - 弹性盒</title>
</head>
<style>
</style>
<body>
</body>
</html>