TextBox com validador de borda vermelha - problema com FOCUS

<asp:textbox ID="txtFocusOK" runat="server" ValidationGroup="FocusOK" /><asp:RequiredFieldValidator ID="valFocusOK" runat="server" ValidationGroup="FocusOK" ControlToValidate="txtFocusOK" SetFocusOnError="true" /><br /><asp:Button ID="btnFocusOK" runat="server" ValidationGroup="FocusOK" Text="Focus OK" /><br /><br /><br /><asp:RequiredFieldValidator ID="valFocusNotOK" runat="server" ValidationGroup="FocusNotOK" ControlToValidate="txtFocusNotOK" SetFocusOnError="true" style="border: 1px solid red"> <asp:textbox ID="txtFocusNotOK" runat="server" ValidationGroup="FocusNotOK" style="visibility: visible" /></asp:RequiredFieldValidator><br /><asp:Button ID="btnFocusNotOK" runat="server" ValidationGroup="FocusNotOK" Text="Focus Not OK" />