alert-on-non-https-links.css

/*
 * Tested with https://add0n.com/stylus.html in Firefox 60
 *
 * Highlight <a> elements with href="http://..."
*/

a[href^="http://"]:before {
  content: "[!]";
  color: red;
}

a[href^="http://"]:focus:before,
a[href^="http://"]:hover:before {
  content: "Link is not HTTPS!";
  position: absolute;
  padding: 10px;
  display: inline-block;
  margin-top: -60px;
  font-size: 20px;
  border: 2px solid red; 
  color: red;
  background-color: #fee;
}