You can customize/translate this system message text: APEX.CORRECT_ERRORS
Others on this list can probably give step by step instructions for doing that if needed.
Keep in mind that this message is shown for any client side validation errors not just missing a required field.
Thank you for reply, but if i want to custom message depending on the specific fields, how can i do ?
Maybe you are looking for a validation?
A validation checks if a certain condition is TRUE or FALSE.
And then it returns the error message. This message can be connected with a field.
See this: Understanding Validations
Thank you for all