The author cites Williams. Is it plagiarism to discuss someone else's work? The blogosphere would look pretty empty.

"There are at least four key principles of visual design that have an important impact on usability. These four principles — contrast, repetition, alignment and proximity — were originally given the engaging acronym CRAP by Robin Williams (the visual designer, not the comedian). You can exploit these four principles to make user interfaces both more attractive and easier to use.

Let’s look at each one in turn."