Over the last years of web programming, I've noticed how bad I am at designing things. I have substantial knowledge of HTML and CSS, I can make a website look like I want it to, I have some pretty intense knowledge about usability. My only problem is: I can't design a web-site or even an element of it to look good and solid. Either the colors are wrong or the spacing, I can't pinpoint it most of the time, but something is off every time.
How could I get a better feeling for design matters like compositing or coloring? Could you recommend any books, articles or maybe trainings?