Use this Boolean function to determine whether a URL is valid:
public static bool checkUrl(string url) { bool rt = false; if (url.StartsWith("www.")) { url = "http://" + url; } HttpWebRequest myRequest = (HttpWebRequest)WebRequest.Create(url); HttpStatusCode code = new HttpStatusCode(); HttpWebResponse myResponse = null; try { myResponse = (HttpWebResponse)myRequest.GetResponse(); code = myResponse.StatusCode; rt = true; } catch(WebException err) { rt = false; } return rt;}