XHTML™ 1.0 The Extensible HyperText Markup Language (Second Edition)

A Reformulation of HTML 4 in XML 1.0

W3C Recommendation 26 January 2000, revised 1 August 2002
superseded 27 March 2018

This version:: http://www.w3.org/TR/2018/SPSD-xhtml1-20180327/
Latest version:: http://www.w3.org/TR/xhtml1
Previous version:: http://www.w3.org/TR/2002/REC-xhtml1-20020801
Diff-marked version:: http://www.w3.org/TR/2002/REC-xhtml1-20020801/xhtml1-diff.html
Authors:: See acknowledgments.

Please refer to the errata for this document, which may include some normative corrections. See also translations.

This document is also available in these non-normative formats: Multi-part XHTML file, PostScript version, PDF version, ZIP archive, and Gzip'd TAR archive.

Abstract

This specification defines the Second Edition of XHTML 1.0, a reformulation of HTML 4 as an XML 1.0 application, and three DTDs corresponding to the ones defined by HTML 4. The semantics of the elements and their attributes are defined in the W3C Recommendation for HTML 4. These semantics provide the foundation for future extensibility of XHTML. Compatibility with existing HTML user agents is possible by following a small set of guidelines.

Status of this document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. The latest status of this document series is maintained at the W3C.

This specification is a Superseded Recommendation. A newer specification exists that is recommended for new adoption in place of this specification. New implementations should follow the latest version of the HTML specification.

This document is the second edition of the XHTML 1.0 specification incorporating the errata changes as of 1 August 2002. Changes between this version and the previous Recommendation are illustrated in a diff-marked version.

This second edition is not a new version of XHTML 1.0 (first published 26 January 2000). The changes in this document reflect corrections applied as a result of comments submitted by the community and as a result of ongoing work within the HTML Working Group. There are no substantive changes in this document - only the integration of various errata.

At the time of publication, the working group believed there were zero patent disclosures relevant to this specification. A current list of patent disclosures relevant to this specification may be found on the Working Group's patent disclosure page.

A list of current W3C Recommendations and other technical documents can be found at https://www.w3.org/TR/.

Quick Table of Contents

Full Table of Contents

1. What is XHTML?
- 1.1. What is HTML 4?
- 1.2. What is XML?
- 1.3. Why the need for XHTML?
2. Definitions
- 2.1. Terminology
- 2.2. General Terms
3. Normative Definition of XHTML 1.0
- 3.1. Document Conformance
  - 3.1.1. Strictly Conforming Documents
  - 3.1.2. Using XHTML with other namespaces
- 3.2. User Agent Conformance
4. Differences with HTML 4
- 4.1. Documents must be well-formed
- 4.2. Element and attribute names must be in lower case
- 4.3. For non-empty elements, end tags are required
- 4.4. Attribute values must always be quoted
- 4.5. Attribute Minimization
- 4.6. Empty Elements
- 4.7. White Space handling in attribute values
- 4.8. Script and Style elements
- 4.9. SGML exclusions
- 4.10. The elements with 'id' and 'name' attributes
- 4.11. Attributes with pre-defined value sets
- 4.12. Entity references as hex values
5. Compatibility Issues
- 5.1. Internet Media Type
A. DTDs
- A.1. Document Type Definitions
  - A.1.1. XHTML-1.0-Strict
  - A.1.2. XHTML-1.0-Transitional
  - A.1.3. XHTML-1.0-Frameset
- A.2. Entity Sets
  - A.2.1. Latin-1 characters
  - A.2.2. Special characters
  - A.2.3. Symbols
B. Element Prohibitions
C. HTML Compatibility Guidelines
- C.1. Processing Instructions and the XML Declaration
- C.2. Empty Elements
- C.3. Element Minimization and Empty Element Content
- C.4. Embedded Style Sheets and Scripts
- C.5. Line Breaks within Attribute Values
- C.6. Isindex
- C.7. The lang and xml:lang Attributes
- C.8. Fragment Identifiers
- C.9. Character Encoding
- C.10. Boolean Attributes
- C.11. Document Object Model and XHTML
- C.12. Using Ampersands in Attribute Values (and Elsewhere)
- C.13. Cascading Style Sheets (CSS) and XHTML
- C.14. Referencing Style Elements when serving as XML
- C.15. White Space Characters in HTML vs. XML
- C.16. The Named Character Reference '
D. Acknowledgements
E. References