//If you have users enter URLs and you would like to check them to make sure they exist before you //save them to the database, here is the code:
<%@ Page Language="C#" %>
<%@ Import Namespace="System.Net" %>
<%@ Import Namespace="System.Net.Sockets" %>
<script runat="server">
    public void Page_Load(Object sender, EventArgs E) {
      string url = "www.google.com";
      if(UrlIsValid(url)) {
         Response.Write("The URL '" + url + "' is valid.");
      } else {
         Response.Write("The URL '" + url + "' is NOT valid.");
      }
    }
   public static bool UrlIsValid(string smtpHost)
   {
      bool br = false;
      try {
         IPHostEntry ipHost = Dns.Resolve(smtpHost);
         br = true;
      }
      catch (SocketException se) {
         br = false;
      }
      return br;
   }
script>