W3C CSS Validator API

The W3C CSS Validation Service is a free software created by the W3C to help Web designers and Web developers check Cascading Style Sheets (CSS). It compares user style sheets to the CSS specifications, helping to find errors, typos, or incorrect uses of CSS, it will also tell when the user's CSS poses some risks in terms of usability. The API uses SOAP protocol and responses are formatted in XML.