Please help! I don't know why its not running

Tell us what’s happening:

Your code so far


<!DOCTYPE html>
<html>
    <h1>Hell</h1>
</html>

Your browser information:

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.140 Safari/537.36 Edge/17.17134.

Link to the challenge:
https://learn.freecodecamp.org/responsive-web-design/basic-html-and-html5/declare-the-doctype-of-an-html-document