HTML validation – SEO WIKI
Validation is a check of a document for errors and for its correctness as a whole. Thus, a web document that has passed this procedure and has no comments on the code is called valid.
HTML follows a set of rules called a specification. Develops the W3 Consortium Specification (www.w3c.org) with support
There are several reasons to take care of validating an HTML document:
Correctness – a valid document will correctly display in a web browser.
Debugging – incorrect code can lead to errors that will not be easy to detect.
Support – a valid document can be updated without problems later, even to another user.