To be considered trustworthy by others, however, you must also give the appearance of trustworthiness. Consistency is the value that says that similar parts of the system should work in the same way. Don't make the user jump through hoops, for instance, by using one navigation scheme on one part of your Web site, and then switching to a radically different method farther in. What the user learns in one situation should be applicable when the same situation appears again. With this kind of consistency, users gain confidence in their understanding of that part of the system, and with that sense of mastery comes confidence in the system as a whole.
Aesthetic integrity is the visual equivalent of behavioral consistency.
This principle says both that the system should hang together as a visual whole, and that the various controls should have a similar appearance throughout the system. Although Web design in particular tends to encourage people to experiment with the look of buttons and other controls, you should make sure that your controls are readily recognizable as such, and that what appears to be a banner graphic on one screen doesn't suddenly become an action button on the next. Perceived stability is the idea that the system should appear stable until the user changes it. When the system appears to be changing without users' knowledge, users lose their sense of control. On those occasions when you do need to perform some sort of automatic process or update, use feedback and dialog to make sure that users are kept informed of what is happening and have been allowed the opportunity to control the process.