<!DOCTYPE html>
<html>
<html lang="en">
<head>
<meta content="text/html;charset=utf-8" http-equiv="Content-Type">
<meta content="utf-8" http-equiv="encoding">
<title>Welcome </title>
<style>
    body {
        width: 35em;
        margin: 0 auto;
        font-family: Tahoma, Verdana, Arial, sans-serif;
    }
</style>
</head>
<body>
<img src="/captcha" alt="loading error!"/>
<form method="POST" action="/captcha">
    <!-- Equivalent to... -->
      <label for="captcha">验证：</label>
  <input type="text" 