the user when they registers.It can be done 
easily by adding OnCreatedUser event in the 
CreateUserWizard control first -
<asp:CreateUserWizard ID="CreateUserWizard1" 
runat="server" CreateUserButtonText="Next" 
OnCreatedUser="CreateUserWizard1_CreatedUser">
.....
then we have to add the following lines in the
CreateUserWizard1_CreatedUser method in code
behind file-Register.aspx.cs as shown below -
protected void CreateUserWizard1_CreatedUser
(object sender, EventArgs e)
{
 Roles.AddUserToRole(CreateUserWizard1.UserName, 
 "registered");
}
here i assigned the role 'registered' to the user.

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