Jeffrey Zeldman in Fear of Style Sheets: “Cascading Style Sheets (CSS) save bandwidth, vastly reducing the size of your files when compared to old-style markup. With styles, your sites load faster. You work faster, too. Styles shave grueling hours of grunt-work off your design workload: one brief CSS document can style an entire domain; and when it’s time to redesign, you can execute site-wide changes in minutes instead of days.
Style sheets bring genuine leading and sophisticated margination to the web, easing our readers’ eyestrain while bringing us the control of negative space we take for granted in other media. They offer exciting new possibilities, from absolute positioning, to interactive manipulation of text and images. And they allow us to create sophisticated layouts while doing no harm to the underlying structure of our documents — ensuring that search engines (as well as hand-held devices, web phones, and other futuristic browser morphs) can “understand” our pages as easily as readers do.”
CSS Cheat Sheet covers the most useful CSS properties with examples.