See the question and my original answer on StackOverflow

Well in this case, you don't need to parse anything, you just need to get an HTTP request and get the stream, like this:

    HttpWebRequest req = (HttpWebRequest)WebRequest.Create("http://www.whatismyip.com/automation/n09230945.asp");
    using (StreamReader reader = new StreamReader(req.GetResponse().GetResponseStream()))
    {
        Console.WriteLine(reader.ReadToEnd());
    }

If you really want to use Html Agility Pack, this is the equivalent:

    HtmlWeb web = new HtmlWeb();
    Console.WriteLine(web.Load("http://www.whatismyip.com/automation/n09230945.asp").DocumentNode.OuterHtml);