asp.net menu control staticBottomSeparatorImage appears underneath horizontal menu

I'm using the ASP menu control, .NET 4.0. I finally got the styles working thanks to the answer on this post but now that I've set the controlRenderingCompatibilityVersion in my web.config to "4.0" I'm seeing my separator image underneath the Menu control.

<div class="menuContain开发者_如何学Pythoner">
        <asp:Menu ID="_menu" runat="server" EnableTheming="true" DataSourceID="_siteMap" CssClass="menuClass" IncludeStyleBlock="false" 
            Orientation="Horizontal" StaticBottomSeparatorImageUrl="../images/menuSepImage.jpg" OnMenuItemDataBound="_menu_OnDataBound">
        </asp:Menu>
        <asp:SiteMapDataSource ID="_siteMap" runat="server" ShowStartingNode="false" />
    </div>

I tried pulling out the default CSS styles that are auto-generated, and setting IncludeStyleBlock="false" but setting the #_menu img.horizontal-separator {} class in my CSS doesn't do anything, which is why I'm trying to set it with the StaticBottomSeparatorImageUrl property.

(Answered in the comment. Converted to a community wiki answer. See Question with no answers, but issue solved in the comments (or extended in chat) )

The OP wrote:

This solved the issue in case anyone else is wondering Add to CSS: .horizontal-separator { position:relative; top:-36px; } And set the height of the div that contains the menu.