FormsAuthentication

Vad kan det vara som gör att denna alltid returnerar false även fast namn å lösen är rätt?

    protected void LoginButton_Click(object sender, EventArgs e)
    {
        Response.Write(FormsAuthentication.Authenticate("namn", "******").ToString());
        Response.End();
    }

		<membership defaultProvider="CustomMembershipProvider" hashAlgorithmType="SHA1">
			<providers>
				<clear/>
				<add name="CustomMembershipProvider" 
					 type="System.Web.Security.SqlMembershipProvider" 
					 connectionStringName="SqlServer" 
					 enablePasswordRetrieval="false" 
					 enablePasswordReset="true" 
					 requiresQuestionAndAnswer="false" 
					 requiresUniqueEmail="true"
					 passwordFormat="Hashed"
					 maxInvalidPasswordAttempts="5"
					 passwordStrengthRegularExpression=""
					 minRequiredPasswordLength="4"
					 minRequiredNonalphanumericCharacters="0"
					 applicationName="labb"/>
				</providers>
		</membership>

		<authentication mode="Forms">
			<forms loginUrl="/"
				   protection="All">
				<credentials passwordFormat="SHA1" />
			</forms>
		</authentication>
		
		<authorization>
			<allow users="*"/>
		</authorization>

Denna returnerar däremot true! :q

Response.Write(Membership.ValidateUser("namn", "******"));