The doctype looks like an empty tag with an empty attribute: <!doctype html>.

Can you put together the doctype?

<html>
<head>
<title>My webpage</title>
</head>
<body>
<h1>My favorite things</h1>
<p>
Raindrops on <em>roses</em><br>
Whiskers on <strong>kittens</strong>
</p>
</body>
</html>
]]>

Make sure to assemble <!doctype html>.