Invalid at-rule syntax Web Standard

Description

The CSS at-rule syntax is wrong.

Help

At rule names:

• Must not have any spaces between @ and the rule name
• Must not start with a digit
• Must not start with a dash followed by a digit

Applicable standards

• CSS Validation

Change history

• 2026.62 Oct 2026 Reported for @supports functions other than selector(), font-tech(), font-format() and at-rule(), and for font-tech() or font-format() keywords not defined in CSS Fonts 4.
• 2026.62 Oct 2026 Reported for @keyframes names that are not allowed: none, default, a CSS-wide keyword, or the empty string.
• 5.28 Dec 2017 Added.

This page describes a web site issue detected by SortSite Desktop and OnDemand Suite.

Rule ID: W3cCssInvalidAtRule