Before action
Prevention is better than correction
- Good interfaces prevent avoidable mistakes.
- Requirements should appear before the error.
- Risky actions need consequence and recovery information.
Weak versus strong
Password
Weak
Say invalid password after submit.
Strong
Show requirements before and during entry.
Payment
Weak
Reveal fees after the user commits.
Strong
Show total cost and whether payment is final.
Delete
Weak
Use a vague confirm dialog.
Strong
Explain what will be deleted and whether undo exists.