W3C Validator
This module provides a Drupal interface to use the W3C Markup Validator.
It also provides a module that validates all the pages on your site and stores the results for later review.
Currently the module only validate nodes and views (page displays) but it's planed to expand it to validate more page types.
You should download the w3c validator script and install it on your own server. For Debian based distributions you can get this by installing the w3c_markup_validator package.
For testing you could use the official W3C validator API endpoint at http://validator.w3.org/check but this is highly discouraged and could be considered abuse of service.
Development sponsored by Alquimia Proyectos Digitales.
