[janpieterz]

In my experience the best way to learn these kind of things is just to try!

You might have a list with ideas (they can even be stupid, or already existing). If not, try to make one, the craziest things can go on there. Then every week try to sit down and make the user interface for them. Look at other websites that offer familiar services and combine them. Learning while practicing putting your ideas into reality has been my best way of getting any real sustained progress in skills!

[klum]

Also, make sure you understand why things happen the way they do. If there's an issue with the layout and you manage to fix this by trying some different things, take the time to figure out why the fix worked--things like the box model, collapsing margins and containing floats are all worth understanding. Your designs will feel less like a fragile house of cards, too...