XHTML Tutorial - 8 pages, including introduction, differences from HTML, syntax, DTD, examples, validation, and a quiz. Also, reference pages provide lists of tags and attributes.

Computer Torture - Lists of brief guidelines for XHTML and for XHTML-Basic. [Author and qualifications are not identified.]

Joe Burns: XHTML - Short page introducing the relationships between XHTML and HTML.

Simon Jessey: Learning XHTML - 5 parts including: page structure; lists; hyperlinks and text formatting; tables; and forms. Suitable for beginners, without prior knowledge of HTML.

Web Developer's Virtual Library (WDVL): Introduction to XHTML - 5 parts: introduction; XML and XHTML; document type definitions; differences from HTML; and document structure.

World Wide Web Consortium (w3c): XHTML Modularization - 7 sections: introduction; terminology; module construction; DTD construction; module examples; mark-up language examples; usage examples.

XHTML Explained - Tutorial explaining what XHTML is, describing its benefits, and providing some guidelines for coding.

XHTML Tips - A collection of help, guidance and tips to assist with web authoring.