无法冻结GridView标头

Question

考虑：

<div class="row">
    <br />
    <div class="col-sm-1">
        HISTORICAL
    </div>

    <div id="G1" class="G1">
        <asp:GridView ID="GridView1" runat="server" HeaderStyle-Width="100px" ShowHeaderWhenEmpty="True" CellPadding="3" Font-Size="8pt" GridLines="Vertical" BackColor="White" BorderColor="#999999" BorderStyle="None" BorderWidth="1px">
            <AlternatingRowStyle BackColor="#DCDCDC" />
            <FooterStyle BackColor="#CCCCCC" ForeColor="Black" />
            <HeaderStyle CssClass="Freezing" Width="100px" BackColor="#000084" Font-Bold="True" ForeColor="White"></HeaderStyle>
            <PagerStyle BackColor="#999999" ForeColor="Black" HorizontalAlign="Center" />
            <RowStyle BackColor="#EEEEEE" ForeColor="Black" />
            <SelectedRowStyle BackColor="#008A8C" Font-Bold="True" ForeColor="White" />
            <SortedAscendingCellStyle BackColor="#F1F1F1" />
            <SortedAscendingHeaderStyle BackColor="#0000A9" />
            <SortedDescendingCellStyle BackColor="#CAC9C9" />
            <SortedDescendingHeaderStyle BackColor="#000065" />
        </asp:GridView>
    </div>

在