Sitemap's sub-menu are hidden behind a JavaScript image Gallery in Asp.net page?

In my asp.net page with sitemap menus and sub-menu is added a java-scripting and jQuery image gallery, but when I go for submenu it is hidden behind the image gallery.

My menu's css code are:

.menuItem
{     
    border:Outset 1px black;
    background-color:Gray;
    font:14px Arial;
    color:White;
    padding:8px;            
}

Menu and SiteMap:

<asp:Menu ID="Menu1"  StaticMenuItemStyle-CssClass="menuItem"
        DynamicMenuItemStyle-CssClass="menuItem" Runat="server" Orientation="Horizontal" DataSourceID="srcSiteMap" /> 
 开发者_如何转开发                               <asp:SiteMapDataSource ID="srcSiteMap" Runat="server" ShowStartingNode="false" /> 

you can fix that with setting both elements

position:relative; //or
position:absolute;

and then giving one element some lower number of

z-index: 0;

and other one some high number like

z-index: 10;

hope it helps.