A problem with HttpWebResponse object to get HTTP Response

[Plato2]

I'm trying to get an HTML content of a remote page. This page accepts Login and Password. I'm trying to pass login and password but HTTP content get returned is not correct.
Any idea why?
Thanks in advance

Dim lcUrl As String = "

https://www.myurl.com/login.aspx"

Dim UserName, UserPwd As String
UserName = "user_name"
UserPwd = "password"
Dim loHttp As HttpWebRequest = WebRequest.Create(lcUrl)
loHttp.AllowAutoRedirect = True
'post data
Dim lcPostData As String = "username=" + HttpUtility.UrlEncode(UserName) + "&password=" + HttpUtility.UrlEncode(UserPwd)
loHttp.Method = "POST"
loHttp.ContentLength = lcPostData.Length

Dim lbPostBuffer As Byte() = System.Text.Encoding.GetEncoding(1252).GetBytes(lcPostData)

loHttp.ContentLength = lbPostBuffer.Length
Dim loPostData As Stream = loHttp.GetRequestStream()
loPostData.Write(lbPostBuffer, 0, lbPostBuffer.Length)
loPostData.Close()
Dim loWebResponse As HttpWebResponse = loHttp.GetResponse()
Dim enc As Encoding = System.Text.Encoding.GetEncoding(1252)
Dim loResponseStream As StreamReader = New StreamReader(loWebResponse.GetResponseStream(), enc)
Dim lcHtml As String = loResponseStream.ReadToEnd()
Response.Write(lcHtml)

loWebResponse.Close()
loResponseStream.Close()