txtbox control aspx

<div class="textbox">
    <label><asp:Literal ID="label" runat="server"></asp:Literal></label>
    <asp:TextBox ID="txtValue" runat="server"></asp:TextBox>
    <asp:RegularExpressionValidator ID="RegularExpressionValidator1" ValidationExpression="([0-1][0-9]|2[0-3]):([0-5][0-9])"
        ControlToValidate="txtValue" ValidationGroup="step1" runat="server" ErrorMessage="Zadejte prosím validní čas ve formátu hh:mm" Display="Dynamic"></asp:RegularExpressionValidator>
    <asp:RequiredFieldValidator ID="RequiredFieldValidator2" ControlToValidate="txtValue" runat="server" ErrorMessage="Toto pole je povinné" Display="Dynamic"
        ValidationGroup="step1"></asp:RequiredFieldValidator>
     <asp:PlaceHolder ID="placeHolder" runat="server"></asp:PlaceHolder>
</div>
v