Parse error

[boris-petrov]

::highlight(a),
::highlight(b),
::highlight(c) {
  background-color: yellow;
  color: black;
}

I get three times Error: CSS: Parse Error. on the three ::highlight lines. I think that's a bug in the CSS-validator.

[Tyler-H]

::highlight is a draft selector, so it should not be expected to parse as currently valid CSS, since it currently isn't.

Note the difference between the current version of the spec: https://www.w3.org/TR/css-pseudo-4/#highlight-selectors and https://drafts.csswg.org/css-pseudo/#highlight-selectors, where ::highlight is present.

[boris-petrov]

I see. I don't see in MDN anywhere mentioned that it's a draft selector though.