W3C Validators:
The Markup Validator - AKA The HTML Validator. Checks documents in formats like HTML and XHTML, SVG or MathML.
Link Checker - Checks anchors (Hyperlinks) in HTML and XHTML to make sure links aren't broken.
CSS Validator - Validates CSS Stylesheets or documents that are using CSS styles.
Specific Tools:
Semantic Extractor - View the semantics of a web page.
RDF Validator - Checks and Validates RDF documents.
Feed Validator - Check the syntax of Atom or RSS feeds.
P3P Validator - Checks to see if site is P3P enabled and controls protocol and syntax of Policy-Reference-File and Policy.
XML Schema Validator - Validates the XML Schema.
For more information on W3C specifications and recommendations please visit the World Wide Web Consortium's site at. http://www.w3.org
