WordPress:WPMU Functions/wpmu validate user signup

Make some verifications about Username and Email.

Localize : wp-includes\wpmu-functions.php

Username validation

• If not empty


• If not illegal names like :
  "www", "web", "root", "admin", "main", "invite", "administrator"


• Number of letters, at least 4 characters


• If is not contain "underscore", the _ character


• If is not only contain number


• If the username already exists in DB

Email validation

• If not listed like bad/unsafe email adress


• If is a valid email : x@x.xx


• If is the validation done


• If the email already exists in DB