a program which checks the syntax of an HTML document against a rigorous specification, as defined in a Document Type Definition (DTD)
a program which knows all the rules in HTML, reads your source document and outputs a list of mistakes
A program that checks web pages for the correctness of their code and indicates any errors.
An automated tool to check that coding used to create web pages is valid. It is important that coding is valid as this can impact on the accessibility of pages. Assistive technology used by disabled users such as screen readers may have problems if coding is invalid. Search engines may also have difficulty indexing pages. Most web editing packages include HTML validators or checkers, alongside spell checkers. Online validators are also available, e.g. W3C HTML validator and Style Sheet Validator.
A program or script which is used to check the validity of HTML markup, or to detect bad or deprecated elements. A validator helps to ensure that the document can be read and used by all browsers and search engines.
A validator is a computer program used to check the validity or syntactical correctness of a fragment of code or document. The term is commonly used in the context of validating HTML, CSS and XML documents or RSS feeds though it can be used for any defined format or language.