You answered your own question.
Quote:
Refused to apply style from 'https://stephengroner.com/path/to/styles.css' because its MIME type ('text/html') is not a supported stylesheet MIME type
The stylesheet mime type is 'text/css':
<style type="text/css">
or if using a link:
<link rel="stylesheet" type="text/css" href="yourStylesheet.css" />