W3C Validation
The Worldwide Web Consortium, more commonly known as the W3C is an international standards body developing key standards and guidelines that ensure interoperability and long-term growth for the Web. To help facilitate this process, the W3C makes available a number of validation tools which analyze the coding of a webpage against a particular standard.
The W3C validators determine whether a document actually follows the rules for the language(s) it uses. A document that passes this process with success is called valid.
The pages of this site are coded according to the W3C's XHTML v1.0 and CSS v2.0 specifications which are the current standards in effect.
Additionally, each page of this site at a minimum conforms with WCAG v1.0 level "A" requirements for page accessibility. WCAG v1.0 is the current guideline in effect as version 2.0 has yet to be ratified. You can think of WCAG guidelines as the cyber equivalent of the Americans with Disabilities Act.
The W3C XHTML validator is located here.
The W3C CSS validator is located here.
There is no single validation service for WCAG guidelines nor is it likely there ever will be. A number of websites offer partial validation. A popular validator is the WAVE validator here.