xhtml-css is a website that helps you check the markup and style validity of web pages. It does this by submiting the urls that you want to check to the W3C Markup and the W3C CSS Validators.
These validators send back validations resulats in SOAP format, which this website internaly consumes in order to produce the result you’re seeing.
How this work? The schema below may be better explaining than words:
Web site | xhtml-css.com
