Used to add @import rule to the related CSSStyleSheet object.
String that represents the location of the source file for the imported style sheet.
Optional. Ordinal index that specifies the requested position of the object in the collection. If this value is not supplied, or if the value is larger than the number of items in the collection, the @import rule is added to the end of the collection.
Long Returns the
zero-based index position of the new imported style sheet.