What is W3C Markup Validation and why it is so important?
Most Web documents are written using markup languages, such as HTML or XHTML. These languages are defined by technical specifications, which usually include a machine-readable formal grammar. The act of checking a document against these constraints is called validation, and this is what the W3C Markup Validation Tool does.
Validating a website is an important step which can dramatically help to improve and ensure your website's quality, and it can save a lot of time and money. The Markup Validator is a free service that helps you to check the validity of websites or web pages separately.
This validator can process documents written in most markup languages. Supported document types include the HTML and XHTML, MathML, SMIL and SVG. As for every computer language, these have their own grammar, vocabulary, and syntax, and every document written with these languages are supposed to follow these rules.
The Markup Validation Service is a validator by the World Wide Web Consortium (W3C).