use of form authentication in asp.net

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http://www.codeproject.com/search.aspx?q=form+authentication+in+asp.net&sbo=kw

use login control over your page and add in web.cofig file <deny users="?"/>
this how u'll use form authentication

ADD AUTHENTICATION TAG IN UR WEB.CONFIG FILE AND PASS THE DEFAULT FORM NAME

You Can Create session, and take ths value on every page and define the roleId, If a user have authentication then he can open tha page, other wise he cannot ope the page, ther is some code with the help of this code you can solve your problem.

string strCurrentRole;
        try
        {
            strCurrentRole = Request.QueryString["RoleId"].ToString();
            if (Session["Admin"] == null || strCurrentRole != "04" || Session["Roles"].ToString().IndexOf("04") == -1)
            {
                Session.RemoveAll();
                Response.Redirect("Default.aspx");
            }
        }
        catch
        {
            Session.RemoveAll();
            Response.Redirect("Default.aspx");
        }

There is role id whic you can define on your page.