If the processing has reached an unexpected condition that needs interaction, a disruptive message alerts the user of a problem. Not any disruptive message concerns a serious problem. Sometimes, the user is just notified that proceeding is dangerous. A typical example is the “Save changes before closing?” alert box that appears when a user tries to close a module with modified content. The adequate presentation method for disruptive information is a modal message dialog.
A modal dialog is a secondary window that interrupts user's current activity and blocks interaction until user either simply acknowledge the information by clicking Ok or decides how to proceed (e.g. Yes/No). Effective error messages inform users that a problem occurred, explain why it happened, and provide a solution so users can fix the problem. Users should either perform an action or change their behavior as the result of an error message.
Modal dialogs are error-prone. An alert dialog that appears unexpectedly or which is dismissed automatically (because the user has developed a habit) will not protect from the dangerous action.
- Avoid disruptive messages; workflow maintenance and, therefore, the prevention of errors should be the primary objective.
- Use modal dialogs only for critical or infrequent, one-off tasks that require completion before continuing. Don’t use modal error message dialogs at the normal work flow to inform or warn the user.
- Use mesage panel for non-critical messages which do not require any further user interaction (typically dialogs with a single "OK" or "Close" button).
- Create specific, actionable, user-centered error messages (Figure 60). Users should either perform an action or change their behavior as the result of the message.
- Provide only a short error message and complement it by a Details button that provides more a detailed explanation in the same error dialog.
- If it makes sense for this kind of error, link from the error dialog to the corresponding page in the help system. Provide a Help button then.
Dialogs in general
- Don’t apply dialog boxes that require the use of a scroll bar.
- Don’t include a menu bar or status bar in dialogs.
- Don’t display more than one owned choice dialog at a time from an owner choice dialog.
- Messages should be:
- Understandable: Phrase your messages clearly, in non-technical terms and avoid obscure error codes.
- Readable: User has to be able to read the message in his/her own pace, think about it, understand it. Adding countdown timers (visible or not) and forcing user to read and understand the message within a few seconds is not acceptable,
- Specific instead of general: If the message is reporting a problem concerning a specific object or application, use the object or application name when referring to it.
- Informative and constructive: Tell the user the reason for a problem and help on how to solve the problem.
- Polite, non-terrifying and non-blaming: Avoid wording that terrifies the user ("fatal", "illegal"), blames him for his behavior, and be polite.
Confirmation Button Labels
- When no further input is required:
- To close a warning or error message that does not require further user interaction, provide a Close button. Do not use an OK button. Users may get confused if they are asked to confirm an error.
- When further interaction is required:
- Use buttons which match the type of statement or question made in the warning or error message. For example, do no ask a Yes/No question but then provide OK/Cancel buttons.
- When the user must choose between two actions to continue:
- Use descriptive button labels instead of standard Yes/No or OK/Cancel buttons. For example, if the user must choose to continue or stop an action, provide the buttons "Continue" and "Cancel".
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