The Inclusive Design Institute at OCAD University have released version 1.2 of AChecker, a free open source program checking the accessibility and code compliance for web sites. The Public AChecker is a web based service for checking single pages, there is also a Download AChecker which can be installed to check pages in bulk.
By default the software tests against WCAG 2.0 (Level Double A). There are options for WCAG 1.0 and for Level Triple A. Also BITV 1.0 (Level 2) and Section 508 Stanca Act.
Code validation checks are optional for HTML and CSS.