9.18 WCAG 2.1 Success Criterion 3.3.3 - Error Suggestion
When a user makes an error and the solution can be identified automatically, always provide the user with a suggestion to fix the error.
Before Rectification
The example above shows an error message that is not helpful enough because it is located at the bottom of the webpage, and does not provide an adequate description of what needs to be corrected.
After Rectification
In contrast, this example shows a message that is located at the top of the webpage and provides a good explanation of what needs to be corrected.
WCAG 2.1 Reference:
https://www.w3.org/WAI/WCAG21/Understanding/error-suggestion