help me solve this Error :-Control 'ContentPlaceHolder1_Gridview1' of type 'GridView' must be placed inside a form tag with runat=server.

<asp:Content ID="Content1" ContentPlaceHolderID="head" Runat="Server">
    <title> Print Reciept</title>
    <link href="ClassicGridView.css" rel="stylesheet" type="text/css" />
    <script type="text/javascript">
        function checkAll(objRef) {
            var GridView = objRef.parentNode.parentNode.parentNode;
            var inputList = GridView.getElementsByTagName("input");
            for (var i = 0; i < inputList.length; i++) {
                var row = inputList[i].parentNode.parentNode;
                if (inputList[i].type == "checkbox" && objRef != inputList[i]) {
                    if (objRef.checked) {
                        inputList[i].checked = true;
                    }
                    else {
                        inputList[i].checked = false;
                    }
                }
            }
        }
    </script>

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

    <div style="margin-left:190px;">
        <h2>
            Print GridView Data As Bill Receipt
        </h2>
        <asp:Button ID="btnPrint" runat="server" CssClass="btn" Style="margin-bottom: 10px;"
            Text="Print Selected Record"  Width="174px" OnClick="btnPrint_Click" />
        <asp:GridView ID="Gridview1" GridLines="None" Width="40%" SkinID="GridviewSkin" AutoGenerateColumns="false"
            runat="server">
            <Columns>
                <asp:TemplateField>
                    <HeaderTemplate>
                        <asp:CheckBox ID="checkAll" runat="server" onclick="checkAll(this);" />
                    </HeaderTemplate>

                    <ItemTemplate>

                           <asp:CheckBox ID="ChkOne" runat="server"></asp:CheckBox>
                            <asp:HiddenField ID="hdnCHKOneID" Value='<%#Eval("fid") %>' runat="server" />

                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Fees Id">
                    <ItemTemplate>

                        <asp:Label ID="Label1" runat="server" Text='<%#Eval("fid") %>'></asp:Label>

                    </ItemTemplate>

                </asp:TemplateField>
                <asp:TemplateField HeaderText="Date">
                    <ItemTemplate>
                        <%#Eval("date") %>
                    </ItemTemplate>


                </asp:TemplateField>
                <asp:TemplateField HeaderText="Registration No.">
                    <ItemTemplate>
                        <%#Eval("regno") %>
                    </ItemTemplate>
                </asp:TemplateField>
                <asp:TemplateField HeaderText="Student Name">

                    <ItemTemplate>
                        <%#Eval("stuname") %>
                    </ItemTemplate>
                </asp:TemplateField>

                 <asp:TemplateField HeaderText="Course Name">

                    <ItemTemplate>
                        <%#Eval("cname") %>
                    </ItemTemplate>
                </asp:TemplateField>

                 <asp:TemplateField HeaderText="Fees">

                    <ItemTemplate>
                        <%#Eval("fees") %>
                    </ItemTemplate>
                </asp:TemplateField>

                 <asp:TemplateField HeaderText="Balance">

                    <ItemTemplate>
                        <%#Eval("balance") %>
                    </ItemTemplate>
                </asp:TemplateField>

            </Columns>
            <HeaderStyle CssClass="HeaderStyle" />
            <RowStyle CssClass="RowStyle" />
            <AlternatingRowStyle CssClass="AltRowStyle" />

        </asp:GridView>
    </div>

</asp:Content>