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

This page excels at clearly communicating the problem in a constructive tone and offers three alternatives to solving the problem.

Even though it is better if the system can be used without documentation, it may be necessary to provide help and documentation. Any such information should be easy to search, focused on the user's task, list concrete steps to be carried out, and not be too large.

While this page is well designed there could be users who would benefit from a help page for this address validation page.

January 2001 UPS Address Validation page.