Podstawy

One simple way to incrementally improve an application is to make it more polite. (...)
What makes a polite application? Generally speaking, the absence of rudeness is all it takes. (...)
Don't interrupt the user's workflow. Javascript alerts, errors that could have been prevented, confirmation messages, unnecessarily complicated interactions, and confusing task flows are all things that show off an application rude nature. (...)
Make it easy for he user to get her job done. Pages with elements strewn all over the place without any sense of uniformity are rude because users have a harder time determining the flow of the interaction. Screens that lack visual structure are rude because users are forced to guess what's important and what isn't. (...)
Don't force the user to understand anything that's not relevant to the job she's doing. Applications that require understanding of the underlying system to be productive are rude because they force users to bend to the whims of developers instead of relying on their own mental models.

(Robert Hoekman, jr.)