Jakob Nielsen's 10 Usability Heuristics

The system should always keep users informed about what is going on through appropriate feedback in reasonable time.

• Visibility of system status

• Consistency and standards

• Error prevention

• Help users recognize, diagnose, and recover from errors

The system should speak the users' language, with words, phrases and concepts familiar to the user, rather than system oriented terms.

• Aesthetics and minimalist design

• Visibility of system status

• Match between system and the real world

• Help and documentation

Users often choose system functions by mistake and will need a clearly marked "emergency exit" to leave the unwanted state without having to go through an extended dialogue. Support undo and redo.

• Match between system and the real world

• Consistency and standards

• Help and documentation

• User control and freedom

Users should not have to wonder whether different words, situations, or actions mean the same thing. Follow platform conventions.

• Consistency and standards

• Match between system and the real world

• Help users recognize, diagnose, and recover from errors

• Help and documentation

Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action.

• Recognition rather than recall

• Flexibility and efficiency of use

• Aesthetics and minimalist design

• Error prevention

Minimize the user's memory load by making objects, actions, and options visible. The user should not have to remember information from one part of the dialogue to another. Instructions for use of the system should be visible or easily retrievable whenever appropriate.

• Visibility of system status

• Match between system and the real world

• Recognition rather than recall

• Error prevention

Accelerators -- unseen by the novice user -- may often speed up the interaction for the expert user such that the system can cater to both inexperienced and experienced users. Allow users to tailor frequent actions.

• Help users recognize, diagnose, and recover from errors

• Flexibility and efficiency of use

• Recognition rather than recall

• Consistency and standards

Dialogues should not contain information which is irrelevant or rarely needed. Every extra unit of information in a dialogue competes with the relevant units of information and diminishes their relative visibility.

• Aesthetics and minimalist design

• Help users recognize, diagnose, and recover from errors.

• Help and documentation

• Match between system and the real world

Error messages should be expressed in plain language (no codes), precisely indicate the problem, and constructively suggest a solution.

• Visibility of system status

• User control and freedom

• Error prevention

• Help users recognize, diagnose, and recover from errors

Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation.

• Recognition rather than recall

• Consistency and standards

• Help and documentation

• Match between system and the real world