CSS is often regarded as the poor relation of HTML and JavaScript. After all it is about nothing more interesting than presentation - but the latest CSS 3 includes features such as animation and 3D that overlap with what you can achieve using JavaScript. 

So if you take it seriously you probably should make an effort to write it correctly. Now there is CSSLint to add to JSLint and others that will scan though your CSS and "hurt your feelings" by pointing out your poor coding. You can try it out by pasting your CSS into the web site, click LINT! and you will see a list of shameful errors that you need to correct listed.

The only problem is that some of the rules used to determine "good CSS" you might want to argue with - the most obvious being "Don't use IDs in selectors". If you want to know the whys and wherefores of the rules in detail then see About CSS Lint.

If you don't agree with the rules the good news is that you can change them. The parser and the rules are all written in JavaScript.  All of the rules use a simple plugin mode and the code is open source see: GitHub . There is also a CSSLint for Node.js that doesn't include a user interface so that you can build it into your own projects.

More Information

csslint.net