CSS-SEXP is a library for writing CSS in S-Expressions. For now there is no documentation so just check out the git repository.
CL-USER> (cssexp:with-css-output (*standard-output*) ((or :div.header :span.large) :size "100%")) div.header, span.large { size: 100%; }
git clone http://common-lisp.net/project/css-sexp/git/css-sexp/.git
The mailing list is css-sexp-devel@common-lisp.net
Sorry for the ironic website.