Error: Ajax Calander Controls stopped working in ASP.Net

bhushan98 says:

   <tr>

                        <td class="style7">

                            Period

                        </td>

                        <td class="style3">

                            &nbsp;<asp:TextBox ID="st_date" runat="server" Width="130px"></asp:TextBox>

                            <asp:CalendarExtender ID="st_date_CalendarExtender" runat="server"

                                Enabled="True" TargetControlID="st_date">

                            </asp:CalendarExtender>

                                 To

                            <asp:TextBox ID="end_date" runat="server" Height="22px"></asp:TextBox>

                            <asp:CalendarExtender ID="end_date_CalendarExtender" runat="server"

                                Enabled="True" TargetControlID="end_date">

                            </asp:CalendarExtender>

 Replace above code with below.

<tr>
    <td class="style7">
        Period
    </td>
    <td class="style3">
        &nbsp;<asp:TextBox ID="st_date" runat="server" Width="130px"></asp:TextBox>
        <asp:CalendarExtender ID="st_date_CalendarExtender" runat="server" PopupButtonID="st_date"
            Enabled="True" TargetControlID="st_date">
        </asp:CalendarExtender>
        &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;To
        <asp:TextBox ID="end_date" runat="server" Height="22px"></asp:TextBox>
        <asp:CalendarExtender ID="end_date_CalendarExtender" PopupButtonID="end_date" runat="server"
            Enabled="True" TargetControlID="end_date">
        </asp:CalendarExtender>