Security :: Authenticate User Logged In One Website And Redirect To Other?

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);
Response.Cookies["UserName"].Expires = DateTime.Now.AddHours(1);
Response.Cookies["Password"].Expires = DateTime.Now.AddHours(1);
}

this is the code for storing values in cookie on click of a button. nw in 2nd application on page load i am using this code.

HttpCookie userName = Request.Cookies.Get("UserName");
HttpCookie password = Request.Cookies.Get("Password");
if (userName != null && password != null)
{
if (Membership.ValidateUser(userName.Value, password.Value))
{
FormsAuthentication.RedirectFromLoginPage(userName.Value, false);
}
}

here m able to get the username nd password but don't how to validate that username and password so that i can skip the login page of this application..m not sure about the code in BOLD above if its rite or worng.. and for Login i am using ASP login Control
in both applications.