为何在ie6中不出现滚动条？

<body>
    <form id="form1" runat="server">
    <div class="container">
        <asp:ScriptManager ID="ScriptManager1" runat="server">
        </asp:ScriptManager>
        <div class="listtop" style=" position:relative;">
        </div>
  
        <asp:UpdatePanel ID="UpdatePanel1" runat="server">
            <ContentTemplate>
            <div>
                <asp:GridView ID="gvList" runat="server" Width="100%" AutoGenerateColumns="false"
                    EmptyDataText="对不起，没有相应的数据可以显示！" CssClass="gv" AllowSorting="True" OnSorting="gvList_Sorting"
                    RowStyle-CssClass="gvRow" AlternatingRowStyle-CssClass="gvAlternatingRow" HeaderStyle-CssClass="gvHeader"
                    OnRowDataBound="gvList_RowDataBound">
                    <RowStyle CssClass="gvRow" />
                    <Columns>
                        <asp:TemplateField HeaderText="全选">
                            <HeaderTemplate>
                                <input type="checkbox" id="cbxAll" onclick="SelectAll(event,'cbxKey')">
                            </HeaderTemplate>
                            <ItemTemplate>
                                <input type="checkbox" id="cbxKey" runat="server" value='<%# Bind("Code") %>' />
                                <asp:Label ID="lbKey" runat="server" Text='<%#Eval("Code").ToString()%>' Visible="false"></asp:Label>
                            </ItemTemplate>
                            <ItemStyle HorizontalAlign="Center" Width="40px" />
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="序号" InsertVisible="False">
                            <ItemStyle HorizontalAlign="Center" Width="40px" />
                            <HeaderStyle HorizontalAlign="Center" />
                            <ItemTemplate>
                                <asp:Label ID="lbID" runat="server" Text='' />
                            </ItemTemplate>
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="名称" SortExpression="Name" InsertVisible="False">
                            <ItemStyle HorizontalAlign="Center" />
                            <HeaderStyle HorizontalAlign="Center" />
                            <ItemTemplate>
                                <asp:Label ID="lblName" runat="server" Text='<%#Eval("Name").ToString()%>'></asp:Label>
                                <asp:HiddenField ID="hfCode" runat="server" Value='<%#Eval("Code").ToString()%>' />
                            </ItemTemplate>
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="管辖公安机关" SortExpression="Police">
                            <ItemStyle HorizontalAlign="Center" />
                            <HeaderStyle HorizontalAlign="Center" />
                            <ItemTemplate>
                                <asp:Label ID="lblOrgan" runat="server" Text='<%#GetOrganName(Eval("Police").ToString())%>'></asp:Label>
                            </ItemTemplate>
                        </asp:TemplateField>
                        <asp:TemplateField HeaderText="桥梁类型">
                            <ItemTemplate>
                                <asp:Label ID="lblType" runat="server" Text='<%# GetTypeName(Eval("Type").ToString()) %>'></asp:Label>
                            </ItemTemplate>
                        </asp:TemplateField>
                                          </Columns>
                    <HeaderStyle CssClass="gvHeader" Font-Bold="False" />
                    <AlternatingRowStyle CssClass="gvAlternatingRow" />
                </asp:GridView>
              </div>
               </ContentTemplate>
                 </asp:UpdatePanel>
    </div>
    </form>
</body>
样式
body
{
width: 100%;
height: 100%;
font-size: 10pt;
font-family: "宋体";
_overflow-y:scorll;
}
.container
{
height: 100%;
width: 100%;
overflow: hidden;
text-align:center;
_overflow-y:scorll;
}