Whenever there is a possibility that a form returns errors, the following items must be provided:
These items must be positioned in one of the following places:
Error messages must be explicit. In other words, the user must understand the cause of the error and be able to identify the field, just by reading the error message.
Suggestions for correcting errors that are caused by entering data in an incorrect format must be provided.
In the two examples above, the error messages are thorough and are accompanied by suggestions for correcting the errors (email format).