You can set the CSS validation options in the post of the called url.
For example, if your css file is at
http://www.team123.com/stylesheets/stylesheet1.cscs,
the css validation link is,
http://jigsaw.w3.org/css-validator/validator?uri=http://www.team123.com/stylesheets/stylesheet1.css&profile=css3&usermedium=all&warning=1&lang=en