Although not directly a solution to your problem, you could consider using a CSS-extension framework for the validation part. I use SASS extensively in all my web projects and find it indispensible when you get used to it. Besides all the fancy mixins and variables features etc. it will also perform a validation of your CSS/SASS markup and report for errors as it is perfectly backwards compatible with regular CSS3. The nice thing is that it works as a Ruby Gem which means that it runs locally and can be integrated with other workflows through either Ruby or the command line (terminal in unix environment).
Take it for a spin: http://sass-lang.com/docs/yardoc/
Run sass style.scss and see what happens.
