<center style="width: 1369px;">
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<contenttemplate>
<asp:Panel ID="Panel2" runat="server" CssClass="modalpnl" Style="display: none;">
<table border="0" cellpadding="0" cellspacing="0" style="padding: 30px 0px 0px 0px;
width: 100%; margin-left: 65px;">
<tr>
<td>
<asp:Button ID="btnclose" runat="server" CssClass="closebtn" OnClick="btnclose_Click"
CausesValidation="false" />
</td>
</tr>
<tr>
<td align="left">
<asp:Label ID="Label2" runat="server" Text="Name" CssClass="lblnormal"></asp:Label>
</td>
<td>
<asp:TextBox ID="txtlo" runat="server" CssClass="txtnormal"></asp:TextBox>
<asp:RequiredFieldValidator ID="RequiredFieldValidator6" runat="server" ErrorMessage="*"
ControlToValidate="txtlo" ValidationGroup="vgfeed"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td align="left">
<asp:Label ID="Label3" runat="server" Text="Mobile" CssClass="lblnormal" />
</td>
<td>
<asp:TextBox ID="txtpass" runat="server" CssClass="txtnormal" />
<asp:RegularExpressionValidator ID="RegularExpressionValidator4" runat="server" ErrorMessage="*"
ControlToValidate="txtpass" ValidationGroup="vgfeed" ValidationExpression="\d{10}"></asp:RegularExpressionValidator>
</td>
</tr>
<tr>
<td>
<asp:Label ID="Label4" runat="server" Text="Email" CssClass="lblnormal" />
</td>
<td>
<asp:TextBox ID="txtemail" runat="server" CssClass="txtnormal_website" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator7" ValidationGroup="vgfeed" ControlToValidate="txtemail"
runat="server" ErrorMessage="*"></asp:RequiredFieldValidator>
<asp:RegularExpressionValidator ID="RegularExpressionValidator5" runat="server" ErrorMessage="*"
ControlToValidate="txtemail" ValidationGroup="vgfeed" ValidationExpression="\w+([-+.']\w+)*@\w+([-.]\w+)*\.\w+([-.]\w+)*"></asp:RegularExpressionValidator>
</td>
</tr>
<tr>
<td>
<asp:Label ID="Label5" runat="server" Text="Comments" CssClass="lblnormal" />
</td>
<td>
<asp:TextBox ID="txtcomments" TextMode="MultiLine" runat="server" CssClass="txtnormal" />
<asp:RequiredFieldValidator ID="RequiredFieldValidator8" runat="server" ControlToValidate="txtcomments"
ErrorMessage="*" ValidationGroup="vgfeed"></asp:RequiredFieldValidator>
</td>
</tr>
<tr>
<td>
<asp:ImageButton ID="btnfeedback_1" runat="server" CssClass="bt_login" OnClientClick="return ShowSuccessMessagereg()"
ImageUrl="images/submit_btn.png" Width="100px" OnClick="btnfeedback_1_Click"
CausesValidation="true" ValidationGroup="vgfeed" />
</td>
<td>
</td>
</tr>
</table>
<asp:LinkButton ID="LinkButton3" runat="server">
</asp:LinkButton>
<ajaxToolkit:ModalPopupExtender ID="popup1" runat="server" DropShadow="false" PopupControlID="Panel2"
TargetControlID="LinkButton3" BackgroundCssClass="modalBackground" CancelControlID="btnclose" >
</ajaxToolkit:ModalPopupExtender>
</asp:Panel>
</ContentTemplate>
<Triggers>
<asp:AsyncPostBackTrigger ControlID="btnfeedback_1" EventName="Click" />
<asp:AsyncPostBackTrigger ControlID="btnclose" EventName="Click" />
<asp:AsyncPostBackTrigger ControlID="LinkButton3" />
</Triggers>
</asp:UpdatePanel>
</center>
by using above coding validations are not supported.