ownerNode returns the node that associates this style sheet with the document.
Syntaxnode = stylesheet.ownerNode
node is an object reference to the element that brings in the stylesheet.
For HTML, ownerNode may be the corresponding LINK or STYLE element. For XML, it may be the linking processing instruction. For style sheets that are included by other style sheets, the value of this attribute is null.
DOM Level 2 Styles - STYLESHEET