<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
<style type="text/css">
body{counter-reset:liu}
.after:after{content:counter(liu)}
input:checked{counter-increment:liu}
</style>
</head>
<body>
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<input type="checkbox">
<span class="after"></span>
</body>
</html>
来源：https://www.cnblogs.com/liuhao-web/p/6379003.html