I was in the store the other day paying for my mobile phone. There was a middle-aged woman in front of me who was trying to pay for her mobile phone with the payment machine. This payment machine was recently installed, so it was difficult for some people to get used to it. Even I saw the machine for the first time. Anyway that woman was nervously trying to pay, however she even couldn’t go further than entering her phone number, since I hadn’t any experience with that machine as well, I advised her to read the manual that was under the button in the bottom of the screen. She got angry when she heard my advice. Then I noticed that she just didn’t fill in the region code, I told her about that, she didn’t listen, got angry and went away.
That was a good example of the "paradox of the active user" stating that users never read manuals, instead they just start using the thing (software or hardware) immediately. Even though they are having problems with that thing they still refuse to read any manuals.
That’s the important thing that should be kept in mind when desiging any kind of user interfaces, from a desktop application to a website. The UI must be self explanatory; there shouldn’t be any need for reading manuals.