Hiding Master page Menu from Content Page based on role

add a web confing file to the folder that contains Master Page and enable the follwing on the web config file. also enable role manager to true

<authorization>
     <allow roles="Administrators" />
     <deny users="*" />
</authorization>

create an admin link like so:

• <a runat="server" id="adminLink" visible="false"
  href="~/Admin/AdminPage">Admin
• <a runat="server" href="~/">Home
• <a runat="server" href="~/About">About

and then in code write this:
protected void Page_Load(object sender, EventArgs e)
{
if (HttpContext.Current.User.IsInRole("Administrator"))
{
adminLink.Visible = true;
}
}