The Master Page menu is now shown with whte background

I have a master page masterpage.master.At the header of this masterpage, there is NavigationMenu. it is showing the user who is currently logining into the system.
The NavigationMenu aspx is:
<asp:Menu ID="NavigationMenu" runat="server" DataSourceID="SiteMapDataSource1" onmenuitemdatabound="NavigationMenu_MenuItemDataBound" Orientation="Horizontal" StaticEnableDefaultPopOutImage="False" staticsubmenuindent="5"> <LevelMenuItemStyles> <asp:MenuItemStyle CssClass="LoginningUserStyle" /> <asp:MenuItemStyle CssClass="SubMenusStyle1" /> <asp:MenuItemStyle CssClass="SubMenusStyle2"/> </LevelMenuItemStyle ...