How to fix this error with my GridView

Question

I have the follow piece of my .aspx page

<div class="StatusImovelFiltros" style="background-color:#f6f6f6;padding:10px;">
    <div class="TituloFiltros">Status do Imóvel</div>
            <%= RetornaFiltros() %>
</div>  



<asp:Panel ID="pnlTabela" runat="server" Visible="false">
<div class="infoGridsemAba">
<div class='AgrupamentoPrincipal' style="background-color:#831611;padding:3px;">
    Imóveis com Proposta</div>
<div class='AgrupamentoSecundario' style="background-color:#ffc274;padding:3px;">
    Abaixo listando seus imóveis com proposta</div>
<asp:GridView ID="grdImoveis" CssClass="StyleGrid" Width="100%" runat="server" AutoGenerateColumns="false" DataSourceID="dsGrid" BorderWidth="0" GridLines="None">
    <AlternatingRowStyle BackColor="White" CssClass="EstiloDalinhaAlternativaGrid"  HorizontalAlign="Center"/>
    <RowStyle CssClass="EstiloDalinhaGrid" HorizontalAlign="Center" />
    <HeaderStyle BackColor="#e2dcd2" ForeColor="#000" CssClass="thGrid" Height="20" />
    <Columns>
        <asp:BoundField HeaderText="Código" DataField="Imovel_Id" />
        <asp:BoundField HeaderText="Tipo" DataField="TipoDsc1" />
        <asp:BoundField HeaderText="(L/V)" DataField="TransacaoSigla" />
        <asp:TemplateField HeaderText="Endereco">
            <ItemTemplate>
                <%# Eval("Descricao") %> <%# Eval("Logradouro") %>, <%# Eval("Numero") %> - <%# Eval("Expr1") %> <%# Eval("Complemento") %>
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField HeaderText="Propostas Ativas" DataField="NumeroProposta" />
    </Columns>
</asp:GridView>
</div>
    <asp:SqlDataSource ID="dsGrid" runat="server" OnSelected="ds_Selected"></asp:SqlDataSource>
</asp:Panel>

A error occurs on the line where i put the <%= RetornaFiltros() %>. The error said that my GridView need a Runat="server".

Why this error occurs ?I have he runat="server" in my gridview.

The Error stack

[HttpException (0x80004005): Controle 'grdImoveis' do tipo 'GridView' deve ser inserido em uma marca de formato com runat=server.]
   System.Web.UI.Page.VerifyRenderingInServerForm(Control control) +8704611
   System.Web.UI.WebControls.GridView.Render(HtmlTextWriter writer, Boolean renderPanel) +40
   System.Web.UI.WebControls.GridView.Render(HtmlTextWriter writer) +33
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.HtmlControls.HtmlContainerControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.WebControls.WebControl.RenderContents(HtmlTextWriter writer) +10
   System.Web.UI.WebControls.WebControl.Render(HtmlTextWriter writer) +32
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer, ICollection children) +134
   System.Web.UI.Control.RenderChildren(HtmlTextWriter writer) +19
   System.Web.UI.Page.Render(HtmlTextWriter writer) +29
   System.Web.UI.Control.RenderControlInternal(HtmlTextWriter writer, ControlAdapter adapter) +27
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer, ControlAdapter adapter) +99
   System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +25
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1266

Answer 1

the error says that the grid must be placed within form tag.

<form runat="server">
    //your grid here
</form>