W3C

The World Wide Web Consortium oversees web standards.

XSL

The eXtensible Stylesheet Language is less popular than CSS.

What is CSS?

Cascading Style Sheets are used to control the presentational aspects of HTML documents. It was created by the World Wide Web consortium to regain control of document markup. Websites designed with external CSS style sheets are more easily maintained than those using internal style sheets as the style code is centralized. CSS reduces website file sizes for faster downloading and provides precision control over web page presentation.