How to implement Form Authentication

<authentication mode="Forms">
      <forms loginurl="Login.aspx" defaulturl="Default.aspx" path="/" protection="All" timeout="30" />
    </authentication>

<authorization>
  <deny users="?" />
</authorization>

<location path="Join.aspx">
  <system.web>
    <authorization>
      <allow users="*" />
    </authorization>
  </system.web>
</location>

<authentication mode="Forms">
      <forms loginurl="Login.aspx" defaulturl="Home.aspx" path="/">
</forms></authentication>
<authorization>
  <deny users="?" />
</authorization>

// Your method to auth User

if (IsAuth)
{

// Create the authentication ticket and store the roles in the custom UserData property of the authentication ticket
 FormsAuthenticationTicket authTicket = new
                                FormsAuthenticationTicket(1, // version
                                 txtUserId.Value,           // user name
                                 DateTime.Now,               // creation
                                 DateTime.Now.AddMinutes(1),// Expiration
                                 false,                      // Persistent
                                 userData,                    // User data      
                                 FormsAuthentication.FormsCookiePath);
// Now encrypt the ticket.
string encryptedTicket = FormsAuthentication.Encrypt(authTicket);
// Create a cookie and add the encrypted ticket to the 
// cookie as data.
HttpCookie authCookie =
new HttpCookie(FormsAuthentication.FormsCookieName,encryptedTicket);
// Add the cookie to the outgoing cookies collection. 
Response.Cookies.Add(authCookie);
// Redirect the user to the originally requested page
Response.Redirect(FormsAuthentication.GetRedirectUrl(txtUserId.Value, true));

}