C# .NET - Screen scraping for asp page from asp.net

 I am using the following code the scrape results from another website which requires a userName and DateofBirth to validate and then return the results. The code works fine in Local PC, but gives error in Production Server . Remote Server returned error:(403) Forbidden .

Please suggest some ways to resolve this.

   HttpWebResponse res;
   System.IO.StreamReader sr;
   System.IO.Stream s;
   byte[] b;
   string postData="Pass=1&UserName=Bob&Dob=03081982&submit1=Submit";
   try{
   
    HttpWebRequest request =  (HttpWebRequest)WebRequest.Create("http://www.xxx.org/Login.asp");

    request.Method = "POST";
    //request.Accept ="*/*";       
    request.ContentType = "application/x-www-form-urlencoded";    
    b = System.Text.Encoding.ASCII.GetBytes(postData);     
    request.ContentLength = postData.Length;
    request.UserAgent ="Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.0; .NET CLR 1.1.4322)";    
    CookieContainer cookies = new CookieContainer();
    request.CookieContainer = cookies;    
    s=request.GetRequestStream();
    s.Write(b, 0, b.Length);         
    Encoding enc=System.Text.Encoding.ASCII;
    WebResponse response = request.GetResponse();    
    StreamReader responseStream = new StreamReader(response.GetResponseStream(),enc);
       
    //StreamReader responseStream = new StreamReader(response.GetResponseStream(),enc,true);
    string responseHtml = responseStream.ReadToEnd();                   
    int resindex=responseHtml.IndexOf("Registration Number:");
    litHTMLfromScrapedPage.Text=responseHtml;
   }
   catch(Exception ex) {
   litHTMLfromScrapedPage.Text=ex.Source + " " +  ex.Message ;
    
   }

that usually means either you aren't logged in (authenticated), or the server is set up to disallow anything except requests having a referer of the page that is "supposed" to be making the request, or possibly that you aren't transmitting a valid UserAgent request header string.