DuplicateEmailErrorMessage in create user wizard is not working

I create  website in wich i use create user wizard for create new account ,I want that user has use one email ID once only ,same email ID can not reuse again 

so i chane the Porperty of DuplicateEmailErrorMessage , but is not working .

<asp:CreateUserWizard ID="CreateUserWizard1" runat="server"
    ContinueDestinationPageUrl="~/home.aspx" Font-Names="Candara"
        ForeColor="#666666" Height="349px" Width="345px"
    CancelDestinationPageUrl="~/home.aspx"  DuplicateEmailErrorMessage="Plz use other email id"
    oncreateduser="CreateUserWizard1_CreatedUser"><ContinueButtonStyle CssClass="buttonstyl" Height="30px" Width="70px" /><CreateUserButtonStyle CssClass="buttonstyl" Height="30px" Width="100px" /><WizardSteps><asp:CreateUserWizardStep runat="server" /><asp:CompleteWizardStep runat="server" /></WizardSteps></asp:CreateUserWizard>

my code look like this

plz help me :)