What is Web Page Validation?
The W3C webpage validator is a free online software that checks the markup validity of Web documents in HTML, XHTML, SMIL, MathML, etc. Content feeds such as RSS feeds, Atom feeds or other document types such as CSS (Cascading Style Sheets), MobileOK content, (and, RDF, P3P, ...) or locating broken links can also gain W3C validation by the use of other available tools.
These languages are defined by technical specifications that are defined within machine-readable formal grammar and volcabulary. Supported document types include the HTML (through HTML 4.01) and XHTML (1.0 and 1.1) family, MathML, SMIL and SVG (1.0 and 1.1, including the mobile profiles).
Organizations may demonstrate that their web pages are valid and free from errors by displaying a badge (or a referring link badge) to check a page status.
Many of the W3C's validation software is available for opensource download at www.w3.org/Status. Developers are welcome to get involved by contributing code to the W3C projects.
Learn more:
Web design