CSS has UTF-signature
Test passes if you see a green box.
Assertion: The user agent uses a UTF-8 signature without an @charset at the beginning of a css stylesheet to indicate that the encoding is UTF-8.
The HTML page is served as ISO 8859-15. The CSS file encoding is established as utf-8 using only the presence of a UTF-8 signature.
The letters shown are for debugging, should the test fail. Visible letters (left) show what was read from the CSS file; letters that appear when highlighted (right) show what they should match in the HTML.