-introductory material (explaining basics) on cascading style sheets which contains many online resources for tutorials, hacks, styles, etc.

the said material online [here]

some resources:
:: W3C [World Wide Web Consortium] css homepage

:: cssbasics.com

:: W3C Schools

:: Zen Garden (css designs for webpages)

:: CSS layout techniques (glish.com)

:: css beauty (css website resource + news + forum)

:: A List Apart (tutorials + resources)

:: CSS play (CSS demos)