Link Tags > Validation

This is a free service that checks web documents in formats like HTML and XHTML for conformance to W3C recommendations and other standards. Can be searched by URL, File Upload, or Direct Input.

Validome, a German organization, offers webmasters and professional developers a fast and reliable validation tool to check their HTML, XHTML, and XML documents for conformity against existing and approved W3C standards.

AIGA was founded as the American Institute of Graphic Arts in 1914. Now it represents more than 19,000 designers. AIGA provides five main functions for designers: information, communication, inspiration, validation, and representation.

w3Schools is a free web development portal with tutorials on web development subjects such as HTML, JavaScript, and many others. There are also numerous examples for users to look at.