flymake-csslint

To use CSSLint with emacs, you will need CSSLint installed and available on
your path. You should be able to do

$ csslint

without problem. To do this, you can install node.js, npm and
csslint by doing the following:

$ apt-get install nodejs # or your distro / OS equivalent
$ curl http://npmjs.org/install.sh | sh
$ npm install -g csslint

flymake-csslint.el is very much based on flymake-jshint.el by
Wilfred Hughes <me@wilfred.me.uk>.