W3C Markup Validation Service

Last updated
Valid XHTML 1.0.svg
Valid CSS.svg
Tag certifying that a website has been checked for well-formed XHTML (above) and CSS (below) markup

The Markup Validation Service is a validator by the World Wide Web Consortium (W3C) that allows Internet users to check pre-HTML5 HTML and XHTML documents for well-formed markup against a document type definition. Markup validation is an important step towards ensuring the technical quality of web pages. However, it is not a complete measure of web standards conformance. [1] Though W3C validation is important for browser compatibility and site usability, it has not been confirmed what effect it has on search engine optimization.

Contents

As HTML5 has removed the use of DTD in favor of a "Living Standard", the traditional Markup Validation Service is not applicable to these formats. Validation is instead performed using an open-source "Nu Validator", an instance of which is provided by W3C. [2]

History

The Markup Validation Service began as The Kinder, Gentler HTML Validator, a project by Gerald Oskoboiny. [1] It was developed to be a more intuitive version of the first online HTML validator written by Dan Connolly and Mark Gaither, which was announced on July 13, 1994. [3]

In September 1997, Oskoboiny began working for the W3C, and on December 18, 1997, the W3C announced its W3C HTML Validator based upon his works. [4] In November 2008, the W3C released the validator.nu HTML5 engine and the ability to check documents for conformance to HTML5. [5]

W3C also offers validation tools for web technologies other than HTML/XHTML, such as CSS, XML schemas, and MathML. [6]

Browser accommodation

Many major web browsers are often tolerant of certain types of error, and may display a document successfully even if it is not syntactically correct. Certain other XML documents can also be validated if they refer to an internal or external DTD.

Limitations

Mark-up validators cannot see the "big picture" on a web page,[ clarification needed ] but they excel at picking up missed closing tags and other technicalities. [6] [7]

DTD-based validators are also limited in their ability to check attribute values according to many specification documents. For example, using an HTML 4.01 DOCTYPE, bgcolor="fffff" is accepted as valid for the "body" element even though the value "fffff" is missing a preceding '#' character and contains only five (instead of six) hexadecimal digits. Also, for the "img" element, width="really wide" is also accepted as valid. DTD-based validators are technically not able to test for these types of attribute value problems.

Pages may not display as intended in all browsers, even in the absence of validation errors and successful display in other browsers. The only way to ensure that pages always display as intended is to test them in all browsers expected to render them correctly. [7]

CSS validation

While the W3C and other HTML and XHTML validators will assess pages coded in those formats, a separate validator like the W3C CSS validator can check that there are no errors in the associated Cascading Style Sheet. CSS validators apply current CSS standards to referenced CSS documents. [7]

See also

Related Research Articles

A document type definition (DTD) is a specification file that contains set of markup declarations that define a document type for an SGML-family markup language. The DTD specification file can be used to validate documents.

<span class="mw-page-title-main">HTML</span> HyperText Markup Language

The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It defines the meaning and structure of web content. It is often assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaScript.

<span class="mw-page-title-main">XML</span> Markup language by the W3C for encoding of data

Extensible Markup Language (XML) is a markup language and file format for storing, transmitting, and reconstructing arbitrary data. It defines a set of rules for encoding documents in a format that is both human-readable and machine-readable. The World Wide Web Consortium's XML 1.0 Specification of 1998 and several other related specifications—all of them free open standards—define XML.

Mathematical Markup Language (MathML) is a mathematical markup language, an application of XML for describing mathematical notations and capturing both its structure and content, and is one of a number of mathematical markup languages. Its aim is to natively integrate mathematical formulae into World Wide Web pages and other documents. It is part of HTML5 and standardised by ISO/IEC since 2015.

<span class="mw-page-title-main">Wireless Markup Language</span> Markup language intended for devices that implement the Wireless Application Protocol specification

Wireless Markup Language (WML), based on XML, is an obsolete markup language intended for devices that implement the Wireless Application Protocol (WAP) specification, such as mobile phones. It provides navigational support, data input, hyperlinks, text and image presentation, and forms, much like HTML. It preceded the use of other markup languages used with WAP, such as XHTML and HTML itself, which achieved dominance as processing power in mobile devices increased.

A HTML editor is a program used for editing HTML, the markup of a web page. Although the HTML markup in a web page can be controlled with any text editor, specialized HTML editors can offer convenience, added functionality, and organisation. For example, many HTML editors handle not only HTML, but also related technologies such as CSS, XML and JavaScript or ECMAScript. In some cases they also manage communication with remote web servers via FTP and WebDAV, and version control systems such as Subversion or Git. Many word processing, graphic design and page layout programs that are not dedicated to web design, such as Microsoft Word or Quark XPress, also have the ability to function as HTML editors.

An HTML element is a type of HTML document component, one of several types of HTML nodes. The first used version of HTML was written by Tim Berners-Lee in 1993 and there have since been many versions of HTML. The current de facto standard is governed by the industry group WHATWG and is known as the HTML Living Standard.

XHTML Basic is an XML-based structured markup language primarily designed for simple user agents, often found in mobile devices such as mobile phones, PDAs, pagers, and set-top boxes..

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.

In web development, "tag soup" is a pejorative for syntactically or structurally incorrect HTML written for a web page. Because web browsers have historically treated structural or syntax errors in HTML leniently, there has been little pressure for web developers to follow published standards, and therefore there is a need for all browser implementations to provide mechanisms to cope with the appearance of "tag soup", accepting and correcting for invalid syntax and structure where possible.

In computing, quirks mode is a technique used by some web browsers for the sake of maintaining backward compatibility with web pages designed for old web browsers instead of strictly complying with W3C and IETF standards in standards mode. This behavior has since been codified in the standard, so what was previously standards mode is now referred to as simply no quirks mode.

RDFa or Resource Description Framework in Attributes is a W3C Recommendation that adds a set of attribute-level extensions to HTML, XHTML and various XML-based document types for embedding rich metadata within Web documents. The Resource Description Framework (RDF) data-model mapping enables its use for embedding RDF subject-predicate-object expressions within XHTML documents. It also enables the extraction of RDF model triples by compliant user agents.

<span class="mw-page-title-main">XHTML Mobile Profile</span> Hypertextual computer language standard

XHTML Mobile Profile is an obsolete hypertextual computer language designed specifically for mobile phones and other resource-constrained devices.

<span class="mw-page-title-main">HTML5</span> Fifth and current version of hypertext markup language

HTML5 is a markup language used for structuring and presenting content on the World Wide Web. It is the fifth and final major HTML version that is a World Wide Web Consortium (W3C) recommendation. The current specification is known as the HTML Living Standard. It is maintained by the Web Hypertext Application Technology Working Group (WHATWG), a consortium of the major browser vendors.

Extensible HyperText Markup Language (XHTML) is part of the family of XML markup languages. It mirrors or extends versions of the widely used HyperText Markup Language (HTML), the language in which Web pages are formulated.

<span class="mw-page-title-main">EPUB</span> E-book file format

EPUB is an e-book file format that uses the ".epub" file extension. The term is short for electronic publication and is sometimes styled ePub. EPUB is supported by many e-readers, and compatible software is available for most smartphones, tablets, and computers. EPUB is a technical standard published by the International Digital Publishing Forum (IDPF). It became an official standard of the IDPF in September 2007, superseding the older Open eBook (OEB) standard.

<span class="mw-page-title-main">CSS HTML Validator</span>

CSS HTML Validator is an HTML editor and CSS editor for Windows that helps web developers create syntactically correct and accessible HTML/HTML5, XHTML, and CSS documents by locating errors, potential problems like browser compatibility issues, and common mistakes. It is also able to check links, check spelling, suggest improvements, alert developers to deprecated, obsolete, or proprietary tags, attributes, and CSS properties, and find issues that can affect search engine optimization.

XHTML+RDFa is an extended version of the XHTML markup language for supporting RDF through a collection of attributes and processing rules in the form of well-formed XML documents. XHTML+RDFa is one of the techniques used to develop Semantic Web content by embedding rich semantic markup. Version 1.1 of the language is a superset of XHTML 1.1, integrating the attributes according to RDFa Core 1.1. In other words, it is an RDFa support through XHTML Modularization.

A document type declaration, or DOCTYPE, is an instruction that associates a particular XML or SGML document with a document type definition (DTD). In the serialized form of the document, it manifests as a short string of markup that conforms to a particular syntax.

References

  1. 1 2 "About the W3C Markup Validation Service". W3C Markup Validation Service. World Wide Web Consortium. Retrieved 2011-05-20.
  2. ↑ "Ready to check - Nu Html Checker". validator.w3.org.
  3. ↑ Connolly, Dan (1994-07-13). "ANNOUNCE: HaL Interactive HTML Validation Service". www-html (Mailing list). Retrieved 2008-06-28.
  4. ↑ Oskoboiny, Gerald (2003-03-22). "History of the Kinder, Gentler HTML Validator" . Retrieved 2008-06-28.
  5. ↑ "What's New at The W3C Markup Validation Service". validator.w3.org. Retrieved 2016-05-31.
  6. 1 2 "About the CSS Validator". World Wide Web Consortium. Retrieved 2012-06-24.
  7. 1 2 3 Castro, Elisabeth: HTML, XHTML & CSS, Sixth Edition, page 345–346. Visual Quickstart Guides, Peachpit Press, 2007. ISBN   0-321-43084-0
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.