Custom Messages

This is really two questions:

1. Where can I edit the messages with the validation of Javascript- i.e. "Must be a valid xxx" the message shows
   
2. Where can I edit the message that message that appears after record added or edited, etc. (the green popup that says "Record Added"). I'd like to add the validation for a phone number to say "Please enter as (555) 555-5555"
   Thanks.
   Larry