2.2.2 [DOM Level 2 - Style] Section 1.3, Interface LinkStyle (introduced in DOM Level 2)
The specification states:
The LinkStyle interface provides a mechanism by which a style sheet can be retrieved from the node responsible for linking it into a document. An instance of the LinkStyle interface can be obtained using binding-specific casting methods on an instance of a linking node (HTMLLinkElement, HTMLStyleElement or ProcessingInstruction in DOM Level 2).
Quirks Mode, IE7 Mode, and IE8 Mode (All Versions)
The LinkStyle interface is not supported.