Clarification needed for validating forms

Hi there

I'm using the latest Data Bridge (1.0.5) with DW CS6 on Mac OSX in case this is relevant.

I have a registration form and am wanting to validate it for certain criteria:

1. Email address is in the email format
2. Two password fields match
3. The email address is not already in the database

I'm really struggling with how the logic works and the documentation isn't helping.

I've used the WA Server Validations behaviour and put in my validations but I'm not absolutely clear how I should set it up although I 'think' I've done it correctly.

I've then written an error message and used the Validations...Show If for the line but this is where I'm really struggling.

Can you give me some information on how this actually works? When I think I've done it right, the message shows all the time. Then I change it and it never shows. I'm wondering if the form is submitted, the validation prevents the record from being inserted but the error is lost?

Some comprehensive info on this would be really helpful. I've also searched these forums to try and find the answer.

Many thanks

Jon