I'm designing a registration page for a portal which which will be used all over Europe. The user has to provide his phone number.
The user can select his country / country code via a drop list and enter his phone number in a text field.
my question is how to bhest indicate the format I want the user to enter for the number - area code with respectively without the (0).
Alternative 1: Add a text field label which shows an example (Please use the following format (030) 123456789
Alternative 2: Prefill the text field witha zero.