Hey guys,

I have a form that is having trouble opening. When trying to load the page, the error occurs:

Server Error in Application '/sisgeti'.

Parser Error

Description: Error parsing a resource required to fulfill this request. Examine the specific details of the parse error and modify the source file accordingly. Parser Error Message: Unknown Server Tag: 'ajaxToolkit:ModalPopupExtender'. Origin Error:

Linha 9:  
Linha 10:     <div>
Linha 11:         <ajaxToolkit:ModalPopupExtender ID="mpeExcluir" runat="server" PopupControlID="panExclusao" CancelControlID="BtnCancelaExclusao" TargetControlID="BtnExcluir" DropShadow="true">
Linha 12:             <Animations>
Linha 13:                 <OnShown><Fadein Duration="0.50" /></OnShown>

Source File: /sisgeti/administrador/cadEditais.aspx    Linha: 11

IVersion Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.7.3770.0

Follow the html:

<%@ Page Title="" Language="VB" MasterPageFile="~/administrador/MasterPage.master" AutoEventWireup="false" CodeFile="cadEditais.aspx.vb" Inherits="administrador_cadEditais" %>

<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit.HTMLEditor" tagprefix="cc1" %>
<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %>

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
</asp:Content>
<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">

    <div>
        <ajaxToolkit:ModalPopupExtender ID="mpeExcluir" runat="server" PopupControlID="panExclusao" CancelControlID="BtnCancelaExclusao" TargetControlID="BtnExcluir" DropShadow="true">
            <Animations>
                <OnShown><Fadein Duration="0.50" /></OnShown>
                <OnHiding><Fadeout Duration="0.75" /></OnHiding>
            </Animations>
        </ajaxToolkit:ModalPopupExtender>
        <asp:HiddenField ID="hfID" runat="server" />
    </div>
    
    <div>
        <asp:ModalPopupExtender ID="mpeAviso" runat="server" PopupControlID="panAviso" CancelControlID="BtnConfirmaAviso" TargetControlID="BtnAvisoOculto" DropShadow="true">
            <Animations>
                <OnShown><Fadein Duration="0.50" /></OnShown>
                <OnHiding><Fadeout Duration="0.75" /></OnHiding>
            </Animations>
        </asp:ModalPopupExtender>

    </div>

Can someone help me? Grateful