This module lets you send some CSS (either standalone or embedded in HTML) to the jigsaw.w3.org CSS validation service. In principal, you can run your own local copy of that service and this module will let you point at it, but I've found Jigsaw to be too complication to run myself (unlike the W3C HTML validator).
The interface is fairly simple: send some CSS, and check $v->is_valid. If false, troll through $v->errors and $v->warnings.
This module's API is superficially similar to the one for WebService::Validator::HTML::W3C, but the small differences are frustrating, so that the two modules cannot be used polymorphically without a half-dozen conditionals to differentiate them. That's really my only complaint. Otherwise, this module deserves to be v1.0 instead of v0.2