From the www.w3c.org

16 October 2001: The World Wide Web Consortium today released the Extensible Stylesheet Language (XSL) 1.0 as a W3C Recommendation. The specification has been reviewed by the W3C Membership, who favor its adoption by industry. Designers use an XSL stylesheet to express how source content should be styled, laid out, and paginated onto a presentation medium such as a browser window, a pamphlet or a book.