Why proxy https gets 403

I would like to ask why the following results appear when proxy https
```
<html>

<head>
	<title>403 Forbidden</title>
</head>

<body>
	<center>
		<h1>403 Forbidden</h1>
	</center>
	<hr>
	<center>openresty</center>
</body>

</html>
```