For a CSS newbie, understanding the concept of the box model is fundamental before one can progress to the next level. But if you've been used to writing code with tables for layout, it can be a difficult concept to wrap your brain around at first. I know, because I've been there. ("I'm not only the CSS club president...")

There are lots of tutorials that explain the box model, with varying amounts of verbiage, and diagrams of varying degrees of complexity. But the simplest and most effective box model demo I've seen comes from Red Melon. I can draw the box model all day long on a whiteboard with red, green, and blue dry-erase markers and still have people staring at me with blank faces. But when I show them the Red Melon example, the figurative lightbulb goes off and they'll say something like, "Oh, okay! I get it now." So if you're a CSS newbie - or if you know one - go check out the Red Melon box model demo right now. Even if you don't know any newbies and can recite the W3C's wordy spec in your sleep, take a look anyway, because the slider thingy is really fun to play with.