parentStyleSheet returns the stylesheet object in which the current rule is defined.
Syntax
var stylesheet = cssRule.parentStyleSheet
Parameters
stylesheet
is a stylesheet object.
Example
if ( bgRule.parentStyleSheet != mySheet ) { // alien style rule! }
Notes
See Gecko DOM Reference:event#DOM_styleSheet_Object for more information about the stylesheet object interface.
Specification
DOM Level 2 Style - cssRule