Providing a text description when user input falls outside the required format or values

Description

The objective of this technique is to provide assistance in correcting input errors where the information supplied by the user is not accepted. When users enter data input that is validated, and input errors are detected, information about the nature and location of the input error is provided in text to enable the users to identify the problem. One approach is to use client-side validation and provide an alert dialog box that describes the error immediately when users enter invalid data in field. Another approach, using server-side validation, is to re-display the form (including any previously entered data), and a text description at the top of the page that indicates the fact that there was an error, describes the nature of the problem, and provides ways to easily locate the field(s) with a problem.

However the text description is provided, it should do one of the following things to assist the user:

Provide examples of the correct data entry for the field,
Describe the correct data entry for the field,
Show values of the correct data entry that are similar to the user's data entry, with instructions to the user as to how to enter one of these correct values should the user choose to do so.

Examples

The user inputs invalid data on a form field. When the user exits the field, an alert dialog appears that describes the nature of the error so the user can fix it.
The user inputs invalid data on a form field and submits the form. The server returns the form, with the user's data still present, and indicates clearly in text at the top of the page that there were input errors. The text describes the nature of the error(s) and clearly indicates which field had the problem so the user can easily navigate to it to fix the problem.
The user inputs invalid data on a form field and attempts to submit the form. Client side scripting detects the error, cancels the submit, and modifies the document to provide a text description after the submit button describing the error, with links to the field(s) with the error. The script also modifies the labels of the fields with the problems to highlight them.

Tests

Procedure

Fill out a form, deliberately enter user input that falls outside the required format or values
Check that a text description is provided that identifies the field in error and provides some information about the nature of the invalid entry and how to fix it.
Check that other data previously entered by the user is re-displayed, unless the data is in a security related field where it would be inappropriate to retain the data for re-display (e.g. password).

Expected Results

#2 and #3 are true