How to generate documentation from css file?

Question

I reference to CSSDoc specification and want to generate comment documentation from css file. The first thought used phpdocumentor tool. When execute phpdoc -o HTML:frames:default -f main.css -t docs command, i got "File not parsed,not a php file" error message. Please tell me how to generate documentation from css file by auto-documentation tools. Should be used Doxygen,JavaDoc tool or write a new parser with existing tools. Thanks~~~~