cookie

Question

Hi All my friends 

I want to write a login page. I want to define a  cookie for maintan username in it and I expect this cooki stay in her\his client computer for her\his next referal( if that cookie there is on her\his computer there is no need to login and i show her\him welcome message)

i use below code but i didn't safe result.the cookie destroy.

code for save cooki in client  

 Response.Cookies("username").Value = txtUserName.Text.Trim

   Response.Cookies("username").Expires = DateTime.Now.AddDays(4)

code for retrive it

 If Not (Page.IsPostBack) Then

            If Request.Cookies("username") IsNot Nothing Then lbluser.Text = Request.Cookies("username").Value 

        End If