Asp Menu Control Not working in ie8

<div class="navi_link">

<asp:Menu ID="menuNavigator" runat="server" DisappearAfter="0" StaticSubMenuIndent="0px"
StaticEnableDefaultPopOutImage="False" DataSourceID="SiteMapDataSource2"
Orientation="Horizontal" StaticDisplayLevels="2"
ItemWrap="True" MaximumDynamicDisplayLevels="4" BorderWidth="0"
BorderStyle="None" Font-Size="16px">


<StaticMenuItemStyle Height="20px" ForeColor="Black"
VerticalPadding="0px" BorderWidth="0" BorderStyle="None" />
<DynamicMenuStyle CssClass="sum_menu" />

<Dynamicmenuitemstyle verticalpadding="0px" font-size="0px" BorderWidth="0" BorderStyle="None" />

<DynamicHoverStyle ForeColor="Blue" Font-Size="16px" />
<DynamicSelectedStyle HorizontalPadding="0px" BorderWidth="0" BorderStyle="None" />

</asp:Menu>
<asp:SiteMapDataSource ID="SiteMapDataSource2" runat="server" />

</div>

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Step2.
Now Go to Css Class
.sum_menu
{
z-index: 1;
}


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Or Stilll not working So Then

Write this code in Head Tag of .aspx Page

<meta http-equiv="X-UA-Compatible" content="IE=EmulateIE7" />