at-rule-no-unknown

Disallow unknown at-rules.

    @unknown (max-width: 960px) {}
/** ↑
 * At-rules like this */

This rule considers at-rules defined in the CSS Specifications, up to and including Editor's Drafts, to be known.

The message secondary option can accept the arguments of this rule.

Options

The following patterns are considered problems:

@unknown {}

The following patterns are not considered problems:

@charset "UTF-8";

@CHARSET "UTF-8";

@media (max-width: 960px) {}

@font-feature-values Font One {
  @styleset {}
}

Given:

["/^--my-/", "--custom"]

The following patterns are not considered problems:

@--my-at-rule "x.css";

@--my-other-at-rule {}

@--custom {}