string URL = "http://www.postimage.org/image.php?v=TsMkyRA";

            HttpWebRequest request = (HttpWebRequest)WebRequest.Create(URL);

            request.Timeout = 1000;

            string data = new StreamReader(request.GetResponse().GetResponseStream()).ReadToEnd();


            var image = "no_image.png";
            var s_text = "<img src='";
            var e_text = "' alt='";
            if (data.IndexOf(s_text) != -1)
            {
                int c = (data.IndexOf(s_text) + s_text.Length);
                image = data.Substring(c, (data.IndexOf(e_text, c) - c));
            }