if statment on a master page to control appearance of a menu option

is it possible to set up some kind of control: if user is logged in, then show the menu button

I am using the template from ASP.NET:
<ul id="menu">                         <li><a runat="server" href="~/">Home</a></li>                         <li><a runat="server" href="~/About">About</a></li>                         <li><a runat="server" href="~/ViewCustomers">Customers</a></li>             &nb ...