Here is an excellent introduction to core values of good design. Read it and check which apply to your site :)

Good visual design offers more than improving people’s attitudes to a design. Good visual design will actually make interfaces easier to use.
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.

Full article: A CRAP way to improve usability | Userfocus.