Projects/Usability/HIG/Messages

Messages

Messages include warnings, error messages, confirmation dialogs, and info messages.

Messages should be:

Understandable. Phrase your messages clearly, in non-technical terms and avoid obscure error codes.
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.

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".

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.

Use dialogs for critical error messages, and when you need to make sure that the user sees the message.

Use info panels for non-critical messages which do not require any further user interaction (typically dialogs with a single "OK" or "Close" button).