Jakob Neilsen talks about Mastery, Mystery, and Misery: The Ideologies of Web Design:

Behind a website's superficial appearance lies its fundamental understanding of user behavior in an interactive service. Choices such as whether the "buy" button is red or orange or whether the navigation menu runs across the top or down the left side are much debated, but make at most a few percent difference in usability. In contrast, the design ideology can make or break a site.

...via elearningpost