Ask HN: I just finished a whole book on HTML/CSS. Now what?

Start building stuff. I never learn tools for the sake of the tool; I learn them for the sake of the project I want to use them on. (I exaggerate slightly. Fun is also a big motivator, and some tools are inherently fun. But my main point stands.)

Build something!!! Maybe just a static site or a make your own Posterous or Tumblr theme. This will be a helpful way to apply what you have read. Reading is fine but the best way to learn is to start coding.

shut up and build a site