CSS Day is a one-day advanced CSS conference.
We are assuming that you already understand the basics of these modules. It's the tiny tricky details, the browser compatibility problems, or the unexpected consequences that will form the core of the presentations.
Not entirely sure you know all you need to know about these modules? Eric Meyer's pre-conference workshop might be the thing for you. Or, if you're looking for a hot topic, Peter Gasston's Responsive Web Design one.