CSS is preprocessed on the server-side

http://pcss.wiq.com.br/
http://www.webresourcesdepot.com/php-driven-css-preprocessor-pcss/

39 Ridiculous Things To Do With CSS3 Box Shadows

http://www.viget.com/inspire/39-ridiculous-things-to-do-with-css3-box-shadows/

CSS: Learn: 5 Baby Steps To Learning CSS & Becoming A Kick-Ass CSS Sorcerer

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http://www.makeuseof.com/tag/5-baby-steps-learning-css-kickass-css-sorcerer/

The Next Steps On The Road To Becoming A CSS Jedi Master

http://www.makeuseof.com/tag/steps-road-css-mastery/

Five Useful Interactive CSS/jQuery Techniques Deconstructed

http://coding.smashingmagazine.com/2011/06/16/five-useful-interactive-css-jquery-techniques-deconstruted/

A Guide to CSS Colors in Web Design

http://sixrevisions.com/css/colors-webdesign/#more-5502

Color Opacity and Transparency in CSS