readonly DOMString lastStyleSheetSet

readonly DOMString preferredStyleSheetSet

This attribute must return the preferred style sheet set as set by the author. It is determined from the order of style sheet declarations and the Default-Style HTTP headers, as eventually defined elsewhere in the Web Apps 1.0 specification. If there is no preferred style sheet set, this attribute must return the empty string. The case of this attribute must exactly match the case given by the author where the preferred style sheet is specified or implied. This attribute must never return null.

DOMString selectedStyleSheetSet

This attribute indicates which style sheet set is in use. This attribute is live; changing the disabled attribute on style sheets directly will change the value of this attribute.

If all the sheets that are enabled and have a title have the same title (by case-sensitive comparisons) then the value of this attribute must be exactly equal to the title of the first enabled style sheet with a title in the styleSheets list. Otherwise, if style sheets from different sets are enabled, then the return value must be null (there is no way to determine what the currently selected style sheet set is in those conditions). Otherwise, either all style sheets that have a title are disabled, or there are no alternate style sheets, and selectedStyleSheetSet must return the empty string.

Setting this attribute to the null value must have no effect.

Setting this attribute to a non-null value must call enableStyleSheetsForSet() with that value as the function's argument, and set lastStyleSheetSet to that value.

From the DOM's perspective, all views have the same selectedStyleSheetSet. If a UA supports multiple views with different selected alternate style sheets, then this attribute (and the StyleSheet interface's disabled attribute) must return and set the value for the default view.

readonly nsIDOMDOMStringList styleSheetSets

This must return the live list of the currently available style sheet sets. This list is constructed by enumerating all the style sheets for this document available to the implementation, in the order they are listed in the styleSheets attribute, adding the title of each style sheet with a title to the list, avoiding duplicates by dropping titles that match (case-sensitively) titles that have already been added to the list.