Tell us what’s happening:
I keep getting the “your code should have a !DOCTYPE html declaration” error, despite my code including everything requested in Step 1.
Your code so far
<!-- User Editable Region -->
<!DOCTYPE html>
<html lang="en">
<head></head>
<body></body>
</html>
<!-- User Editable Region -->
Your browser information:
User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:136.0) Gecko/20100101 Firefox/136.0
Challenge Information:
Learn the CSS Box Model by Building a Rothko Painting - Step 1
It appears to be an issue with your browser. You should disable all extensions.
I tried the same on Chrome with no extensions and still got the same error.
That code just passed for me on my computer. Try private mode.
Just tried on private mode (Firefox and Chrome), same error 
Sounds like some strange broad problem with your entire computer? Very odd
I closed the browser, opened it again, enabled all extensions and now it works. Really weird.
I also added freecodecamp.org as an exception to all my extensions, just in case. So far so good.