This document provides an overview of style sheets and how they are used to format XML documents. It discusses Cascading Style Sheets (CSS) and Extensible Stylesheet Language (XSL), the two main standards for styling XML. CSS is used to separate presentation from structure in HTML and XML documents. XSL consists of XSL Transformations (XSLT) for transforming XML documents into other formats, and XSL Formatting Objects (XSL-FO) for formatting XML documents. The document provides examples of using CSS and XSLT to style XML documents.