typography - What are footnotes called when they aren’t in the footer?

What do you call the little asides found in the margins of books instead of at the bottom of the page?

I don’t mean the stuff scribbled in by hand, but rather the printed matter used by tasteful authors who have generous margins and which they put to good use.

Answer

Sidenotes is a common term used to denote the notes, trivia or anything interesting noted by the author on the sidelines of pages of his book. http://en.m.wiktionary.org/wiki/sidenote

At least one author, Robert Bringhurst in his book "The Elements of Typographic Style" has talked about the importance of sidenotes and their formatting issues.