Data submitted in a form is usually validated in some way. And if there is any unacceptable data, the form is traditionally re-displayed, together with validation messages. In such a case, it is important to immediately inform screen reader users, so they know that they have to look at their data and submit again.
Here are the form validation messages explained:
Required Message: The user can't leave this field blank.
Invalid Email: Email address that doesn't have the correct format or doesn't exist anymore.
Invalid URL: A URL contains invalid characters.
Invalid Date: The mentioned date is not correct, it is either past or not in the right format.
Invalid Number: A number that doesn't have the proper format or comes from an invalid area codes.
Invalid Digits: The digits mentioned are not correct.
Invalid Phone: The phone number mentioned doesn't exist or is not in the proper format.
Max Characters: Restricts the total number of characters a respondent can enter into the form.
Min Characters: Requires a minimum number of characters be entered in the form.
Max Words: Restricts the total number of words entered by a respondent in the form.
Min Words: Allows to require that the respondent enter a minimum number of words in the form.
Range: Sets restrictions on what numbers are accepted.