Valid CSS identifiers

The CSS 2.1 recommendation states:

In CSS, identifiers (including element names, classes, and IDs in selectors) can contain only the characters [a-zA-Z0-9] and ISO 10646 characters U+00A0 and higher, plus the hyphen (-) and the underscore (_); they cannot start with a digit, two hyphens, or a hyphen followed by a digit.

List of XML and HTML character entity references (Wikipedia)

my°highlight my§highlight my€highlight myßhighlight myähighlight myöhighlight myühighlight

my¦highlight my•highlight my♠highlight my♥highlight my∴highlight my→highlight my⊳highlight

my🙂highlight my☠highlight