how to authenticate a user who logged in one website nd redirect him to other website without again logging in using cookies

hiii thr... i want to interlink between 2 applications of mine.. suppose a user has logged in one of my application and me store his username and password in cookies...nd nw i want to use those values in the cookies to log-in in other website without entering the username and password again for the other website. i mean to i want to skip the login page of other website.
protected void btnclick_Click(object sender, EventArgs e)
        {
            HttpCookie username = new HttpCookie("UserName", "a");
            HttpCookie password = new HttpCookie("Password", "a");
            Response.Cookies.Add(username);
            Response.Cookies.Add(password);
&nb ...