<form id="pos" runat="server">    
    <p>
        Inserire l'importo e premere 'Acquista'; confermare premendo su 'Continua'.</p>
    <asp:HiddenField ID="txntype" Value="sale" runat="server" />
    <asp:HiddenField ID="timezone" Value="CET" runat="server" />
    <asp:HiddenField ID="txndatetime" Value="" runat="server" />
    <asp:HiddenField ID="hash" Value="" runat="server" />
    <asp:HiddenField ID="storename" Value="000000000" runat="server" />
    <asp:HiddenField ID="mode" Value="payplus" runat="server" />
    <asp:HiddenField ID="currency" Value="978" runat="server" />
    <asp:HiddenField ID="language" Value="it_IT" runat="server" />
    <asp:HiddenField ID="chargetotal" Value="" runat="server" />
    <asp:HiddenField ID="responseSuccessURL" Value="" runat="server" />
    <asp:HiddenField ID="responseFailURL" Value="" runat="server" />
    <asp:TextBox ID="importo" Text="10" runat="server" />
    <asp:Label ID="conferma_importo" Text="Procedi con il pagamento di EUR " runat="server" />
    <asp:Button ID="check" runat="server" Text="Acquista" OnClick="Invia" />
    <asp:Button ID="send" runat="server" Text="Continua" PostBackUrl="https://sitopagamento-online" />
    </form>