Sometimes when you have menu sub-items in a .NET menu control they will be hidden behind an image if they happen to overlap. To fix this, set the z index of the dynamicMenu css class

<%@ Control Language="C#" AutoEventWireup="true" CodeBehind="menu.ascx.cs" Inherits="YANKEE_WEB.menu" %>
<asp:Menu ID="mnuYANKEE" runat="server" DataSourceID="SiteMapDataSource1" 
            Orientation="Horizontal" ForeColor="#8D4F59" Font-Names="Arial" 
                Font-Size="Medium" Font-Bold="True" 
                StaticBottomSeparatorImageUrl="~/Images/separator.gif" 
                StaticEnableDefaultPopOutImage="False" 
                DynamicBottomSeparatorImageUrl="~/Images/Menu_bottom_sep.jpg" 
                CssClass="menumain" onprerender="mnuYANKEE_PreRender" DynamicHoverStyle-BackColor="#CCCCFF">
            <StaticMenuStyle HorizontalPadding="4px" />
            <StaticSelectedStyle ForeColor="#8D4F59" />
            <StaticMenuItemStyle HorizontalPadding="15px" />
            <DynamicHoverStyle BackColor="#cdcdcd" ForeColor="#500000" Font-Overline="False"
                                Font-Underline="false" Font-Bold="true"/>
            
            <DynamicMenuStyle BackColor="#FFFFFF" BorderColor="" CssClass="dynamicMenu" VerticalPadding="0px" HorizontalPadding="0px" />
            <DynamicMenuItemStyle Width="200px" CssClass="dynamicMenuItem" Font-Size="5pt" ForeColor="#8D4F59" />
            <StaticHoverStyle ForeColor="#500000" />
            <Items>
                <asp:MenuItem Text="Home" Value="Home"></asp:MenuItem>
            </Items>
</asp:Menu>

Now the css class for the DynamicMenuStyle

.dynamicMenu {
    text-align:left;
    padding-left:0px;
    font-size:small;
    margin-left:15px;
    margin-top:5px;
    z-index:1000;
}