I have been making my way through The Design of Everyday Things by Donald A. Norman, a book that tries to bridge the gap between the functionality of objects and the way users interact with them. It was originally published in 1988 (which makes for some slightly dated but charming references, such as an in-depth discussion of the hold feature of a new phone system), but the principles are still relevant today in user-centered design theory.
According to Steve Krug, the author of Don’t Make Me Think: A Common Sense Approach to Web Usability, the No. 1 rule of web design is to make the user think as little as possible. Not because the user will leave the site or think it’s poorly designed, but because the user will think it’s their fault if they don’t understand what to do on a website. I think it’s fair to say this is not how we’d like our users to feel upon visiting (or leaving) our sites.