The green/red text should not show until something (at least 3 characters maybe?) has been typed into the Username box. The same goes for Email Address, Password and Confirm Password.
Also, I suggest making the following changes:
Username must be between 3 and 20 long and use alphanumeric, space or -+_ characters.>
This is not a valid username.(the criteria can already be seen on the left, duplicate/repeated text is never good )
The given username can be taken.>
This username can be taken.
The input is not a valid E-Mail address!>
This is not a valid e-mail address.
The given E-Mail address can be taken.>
This e-mail address can be taken.
The given passwords are the same.>
The passwords match.