Ensure that you have fonts that can represent all characters on the lower line of text in the test box. Ensure that the default encoding for the browser you are testing is not set to UTF-8.
Test passes if the lines below look the same
Assertion: A page with no encoding declarations, but with a UTF-8 signature will be recognized as UTF-8.
No encoding information is declared in the HTTP header or inside the document.
The text contains the following sequence of bytes: 0xC3 0xBD 0xC3 0xA4 0xC3 0xA8. The characters serve to distinguish ISO 8859-15 from ISO 8859-1 and UTF-8.
The graphic on the lower line shows what you would expect to see if the page is encoded as UTF-8. The large symbol indicates whether the characters on the two lines should be the same (equal sign) or different (not-equal sign).