あなたはそのように働きたくありません。そのフォームが Post リクエストでサーバーに送信され、値が渡された後のサイトの動作をシミュレートする必要があります。Fiddler2 を使用してフォーム送信を通常どおり実行し、次に以下のように合計することで、サイトの機能を評価できます。
HttpWebRequest request;
HttpWebResponse response;
var responseData = "";
var strUrl = "https://auctions.godaddy.com/trpSearchResults.aspx";
var postData = string.Format("action=review_selected_add&items={0}_B_{1}_1|&rnd={2}&JlPYXTX=347bde7", auctionRef, bid,
randomDouble(0, 1).ToString("0.00000000000000000"));
request = (HttpWebRequest)WebRequest.Create(strUrl);
request.Method = "POST";
request.ContentType = "application/x-www-form-urlencoded";
request.ContentLength = postData.Length;
request.Accept = "text/html, application/xhtml+xml, */*";
request.Accept = "image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/msword, application/vnd.ms-powerpoint, application/vnd.ms-excel, application/x-silverlight, application/x-silverlight-2-b2, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, */*";
request.UserAgent = "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.11 (KHTML, like Gecko) Chrome/23.0.1271.97 Safari/537.11";
request.Headers.Add("Accept-Encoding", "deflate");
request.Referer = "auctions.godaddy.com";
request.Headers["my-header"] = "the-value";
request.KeepAlive = true;
request.CookieContainer = cookies;
request.Timeout = Timeout.Infinite;
var stOut = new StreamWriter(request.GetRequestStream());
stOut.Write(postData);
stOut.Flush();
stOut.Close();
stOut = null;
response = (HttpWebResponse)request.GetResponse();
response.Cookies = request.CookieContainer.GetCookies(request.RequestUri);
var encoding = new System.Text.UTF8Encoding();
var responseReader = new StreamReader(response.GetResponseStream(), encoding, true);
encoding = new System.Text.UTF8Encoding();
responseReader = new StreamReader(response.GetResponseStream(), encoding, true);
responseData = responseReader.ReadToEnd();
response.Close();
responseReader.Close();
上記を使用してデータを投稿するクラスを作成し、html を返すだけです。