XHTML Reference
- An XHTML reference with articles describing HTML-compatibility.
- http://xhtml.com/

New Architect
- Article exploring the issues involved in migrating from HTML to XML.
- http://www.ddj.com/dept/architect/184413727

Marking up documents in XHTML
- The HTML Writers Guild article, detailing the main differences between HTML and XHTML.
- http://gutenberg.hwg.org/markupXHTML.html

XHTML Web Design for Beginners
- An introductory article for those with no prior experience of HTML. Covers version 1.0 Transitional.
- http://www.miswebdesign.com/resources/articles/web-design-xhtml-1-1.html

XHTML :: How to succeed
- Tips and caveats on HTML to XHTML migration for existing browsers.
- http://ptaff.ca/xhtml/?lang=en_CA

XHTML is the Most Important XML Vocabulary
- An article covering possible future outcomes for version 2 of the standard.
- http://www.xml.com/pub/a/2003/05/21/deviant.html

XDG: XHTML Design Guide
- Introduction, tutorial, standards documents, and links to articles.
- http://www.onaicul.com/xdg.html

NYPL Styleguide
- XHTML 1.0 overview. Includes discussion of accessibility and document validation. Also XHTML authoring tips and tools featuring the use of Dreamweaver.
- http://www.nypl.org/styleguide/xhtml/

XHTML: Where XML and HTML meet
- Discussion of XHTML 1.0 and how it improves on the HTML 4.0 standard. Examines the issues involved in the transition between HTML and XHTML. Also explores backwards compatibility to HTML and XHTML modularization.
- http://www.webreference.com/xml/column6/