Users like to explore an interface and often learn by trial and error. An effective interface allows for interactive discovery. It provides only appropriate sets of choices and warns users about potential situations where they may damage the system or data, or better, makes actions reversible or recoverable.
Even within the best designed interface, users can make mistakes. These mistakes can be both physical (accidentally pointing to the wrong command or data) and mental (making a wrong decision about which command or data to select). An effective design avoids situations that are likely to result in errors. It also accommodates potential user errors and makes it easy for the user to recover.
For information about applying the principle of forgiveness, see Chapter 12, "User Assistance," which provides information about supporting discoverability in the interface through the use of contextual, task-oriented, and reference forms of user assistance. For information about designing for the widest range of users, see Chapter 14, "Special Design Considerations."