How/ Is it possible to access Content Ids inside CSS

Question

How to access ASP:Content IDs or ASP:ContentPlaceHolder IDs inside a CSS without using DIV tags in order to apply styles. I tried this using normal CSS Syntax but it didn't work. I need to apply styles to content place holder. Thanks

  <asp:Content ID="Content2" ContentPlaceHolderID="MainContentPlaceHolder"
  runat="server">
     <asp:UpdatePanel runat="server" ID="AdminUpdatePanel">
        <ContentTemplate>
            <table>