The CSS Object Model (CSSOM), part of the DOM, exposes specific interfaces allowing manipulation of a wide amount of information regarding CSS. Initially defined in the DOM Level 2 Style recommendation, these interfaces forms now a specification, CSS Object Model (CSSOM) which aims at superseding it.
The CSSMediaRule is an interface representing a single CSS @media rule. It implements the CSSConditionRule interface, and therefore the CSSGroupingRule and the CSSRule interface with a type value of 4 (CSSRule.MEDIA_RULE).
The StyleSheet.disabled property indicates whether the style sheet is prevented from applying to the document. A style sheet may be disabled by manually setting this property to true or if it's an inactive alternative style sheet. Note that disabled == false does not guarantee the style sheet is applied (it could be removed from the document, for instance).