Returns the preferred style sheet set as set by the page author.
Syntax
preferredStyleSheetSet = document.preferredStyleSheetSet
On return, preferredStyleSheetSet indicates the author's preferred style sheet set. This is determined from the order of style sheet declarations and the Default-Style HTTP header.
If there isn't a preferred style sheet set defined by the author, the empty string ("") is returned.
Example
if (document.preferredStyleSheetSet) {
console.log("The preferred style sheet set is: " + document.preferredStyleSheetSet);
} else {
console.log("There is no preferred style sheet.");
}