Markup language validating system
Whereas HTML pages MAY be thus "enhanced", they SHOULD NOT be dependent on proprietary markup.Specifically, all key functionality and information SHOULD be available to an HTML-compliant browser not supporting the "extension".Following PSS-05, the following Standard Practices are defined: Authors using a DTD other than the above SHALL include an appropriate DOCTYPE declaration.In the case of a DTD that is NOT standard or widely-known (eg those available from Web Techs validation service), the DTD itself SHALL be referenced in a comment within the document. Such notes MAY be delivered separately to the HTML documents (provided they are referenced by a comment in the source), and SHOULD describe the purpose of the invalid construct, together with its effect in several browsers including text-mode browsers (the comment "no effect" is acceptable).These Web Authoring standards should be seen as complementary to the HTML Markup standards published by W3C.These standards shall apply to all webpages created to be accessible to the general public, except as follows: Professional Web developers working for or on behalf of any organisation whose business is not the Web itself (i.e.The purpose of these standards is to encourage compliance with Standards and Good Practice in Web Authoring, and to ensure that authors who deviate from such standards are aware of the consequences of their actions.In particular, it is intended to ensure that systems developed for the World Wide Web are accessible to all users, regardless of their Client software configuration.
It is assumed that readers already have a general working knowledge of HTML, such as might be acquired through appropriate training or experience.
What is W3C Markup Validation and why it is so important?
Most Web documents are written using markup languages, such as HTML or XHTML.
Authors SHOULD NOT use constructs which make assumptions (explicit or otherwise) about a reader's settings.
Examples to be avoided are full-screen tables or divider GIFs whose size is expressed in pixels.