NYPL Online Style Guide

Developed by: New York Public Library
Type of resource: Web guide
Target audience: General
Cost: Free access

"All developers are familiar with HTML, the web’s original markup language. But the W3C currently recommends using XHTML instead. This hybrid language looks and works much like HTML but is based on XML, the web’s “super” markup language." This style guide from the New York Public Library explains the basics and benefits of XHTML, and helps you make the transition painlessly. The guide also includes guidelines on using Cascading Style Sheets (CSS).

http://www.nypl.org/styleguide/