Gravity Forms has filters to allow you to customize the validation and confirmation messages of your forms. If you are using a Bootstrap framework and want to style the messages like alerts, you can use these pieces of code to accomplish that.

Validation Error:

This takes the default validation code and adds the alert and alert-danger class to them via the “gform_validation_message” filter. You could also change up the message itself and be selective on which form you want it to be changed for by putting in logic to determine what $form[‘id’] you are working with.

Confirmation Message:

Similar to the validation error filter above, this wraps the default confirmation in a div with the alert and alert-success Bootstrap classes.