代码示例:(标识:eg_html_form_legend)
<!DOCTYPE html>
<html>
<body>

<form action="/Index/Demo/demo_form.html">
<fieldset>
<legend>Personal information:</legend>
First name:<br>
<input type="text" name="firstname" value="Mickey">
<br>
Last name:<br>
<input type="text" name="lastname" value="Mouse">
<br><br>
<input type="submit" value="Submit">
</fieldset>
</form>

</body>
</html>
运行结果: