fieldset与legend，label
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<fieldset>
<legend>登录</legend>
<label for="username">用户名：</label>
<input id="username" type="text" name="user" />
<br />
<label for="pwd">密码：</label>
<input id="pwd" type="text" name="user" />
</fieldset>
</body>
</html>
