At-rules start with an at-keyword (an '@' character followed immediately by an identifier), and consist of everything up to and including the next semicolon (;) or declaration block, whichever comes first.

At-rules

@charset

Sets the character set for an external style sheet.

@font-face

Sets a font to embed in the HTML document.

@import

Imports an external style sheet.

@media

Sets the media types for a set of rules in a styleSheet object.

@page

Sets the dimensions, orientation, and margins of a page box in a styleSheet.