Web standards are the formal, non-proprietary standards and other technical specifications that define and describe aspects of the World Wide Web. In recent years, the term has been more frequently associated with the trend of endorsing a set of standardized best practices for building web sites, and a philosophy of web design and development that includes those methods.
Web standards include many interdependent standards and specifications, some of which govern aspects of the Internet, not just the World Wide Web. Even when not web-focused, such standards directly or indirectly affect the development and administration of web sites and web services. Considerations include the interoperability, accessibility and usability of web pages and web sites.
Web standards, in the broader sense, consist of the following:
- Recommendations published by the World Wide Web Consortium (W3C)
- "Living Standard" made by the Web Hypertext Application Technology Working Group (WHATWG)
- Request for Comments (RFC) documents published by the Internet Engineering Task Force (IETF)
- Standards published by the International Organization for Standardization (ISO) 
- Standards published by Ecma International (formerly ECMA) 
- The Unicode Standard and various Unicode Technical Reports (UTRs) published by the Unicode Consortium 
- Name and number registries maintained by the Internet Assigned Numbers Authority (IANA) 
Web standards are not fixed sets of rules, but are a constantly evolving set of finalized technical specifications of web technologies. Web standards are developed by standards organizations—groups of interested and often competing parties chartered with the task of standardization—not technologies developed and declared to be a standard by a single individual or company. It is crucial to distinguish those specifications that are under development from the ones that already reached the final development status (in case of W3C specifications, the highest maturity level).
When web standards are discussed, the following publications are typically seen as foundational:
- Recommendations for markup languages, such as Hypertext Markup Language (HTML), Extensible Hypertext Markup Language (XHTML), and Scalable Vector Graphics (SVG) from W3C.
- Recommendations for stylesheets, especially Cascading Style Sheets (CSS), from W3C.
- Recommendations for Document Object Models (DOM), from W3C.
- Properly formed names and addresses for the page and all other resources referenced from it (URIs), based upon RFC 2396, from IETF.
- Proper use of HTTP and MIME to deliver the page, return data from it and to request other resources referenced in it, based on RFC 2616, from IETF.
Work in the W3C toward the Semantic Web is currently focused by publications related to the Resource Description Framework (RDF), Gleaning Resource Descriptions from Dialects of Languages (GRDDL) and Web Ontology Language (OWL).
Standards publications and bodies
A W3C Recommendation is a specification or set of guidelines that, after extensive consensus-building, has received the endorsement of W3C Members and the Director.
An IETF Internet Standard is characterized by a high degree of technical maturity and by a generally held belief that the specified protocol or service provides significant benefit to the Internet community. A specification that reaches the status of Standard is assigned a number in the IETF STD series while retaining its original IETF RFC number.
Non-standard and vendor-proprietary pressures
HTML 5 contains numerous "willful violations" of other specifications, in order to accommodate limitations of existing platforms.
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- "W3C Technical Reports and Publications". W3C. Retrieved 2009-01-19.
- "IETF RFC page". IETF. Retrieved 2009-01-19.
- "Search for World Wide Web in ISO standards". ISO. Retrieved 2009-01-19.
- "Ecma formal publications". Ecma. Retrieved 2009-01-19.
- "Unicode Technical Reports". Unicode Consortium. Retrieved 2009-01-19.
- "IANA home page". IANA. Retrieved 2009-01-19.
- Leslie Sikos (2011). Web standards - Mastering HTML5, CSS3, and XML. Apress. ISBN 978-1-4302-4041-9.
- Berners-Lee, Tim; Fielding, Roy T.; Masinter, Larry (August 1998). Uniform Resource Identifiers (URI): Generic Syntax. IETF. doi:10.17487/RFC2396. RFC 2396. https://tools.ietf.org/html/rfc2396. Retrieved 2009-10-27.
- Fielding, Roy T.; Gettys, James; Mogul, Jeffrey C.; Nielsen, Henrik Frystyk; Masinter, Larry; Leach, Paul J.; Berners-Lee, Tim (June 1999). Hypertext Transfer Protocol -- HTTP/1.1. IETF. doi:10.17487/RFC2616. RFC 2616. https://tools.ietf.org/html/rfc2616. Retrieved 2009-10-27.
- "Web Content Accessibility Guidelines 1.0, W3C Recommendation 5-May-1999". W3C. 1999. Retrieved 2009-02-18.
- "HTML 5 - A vocabulary and associated APIs for HTML and XHTML - Compliance with other specifications". Retrieved 2017-06-29.