Disallow vendor prefixes for @rules.
@-webkit-keyframes { 0% { top: 0; } }
/** ↑
* These prefixes */The following patterns are considered warnings:
@-webkit-keyframes { 0% { top: 0; } }@-ms-viewport { orientation: landscape; }The following patterns are not considered warnings:
@keyframes { 0% { top: 0; } }@viewport { orientation: landscape; }