WebBrowser www = new WebBrowser();

www.Navigate(OAuthUtility.BuildAuthorizationUri(this.t1.Token));
            string verifier;

            rr:

            do
            {
               
                MessageBox.Show("Ждем"); //так работает
                // if (www.DocumentText == "") { goto rr; } //так не работает
                int num3 = 99999;
                while (num3 > 0)
                    --num3;
                HtmlElementCollection elementsByTagName = www.Document.GetElementsByTagName("small");
                verifier = "";
                foreach (HtmlElement htmlElement in elementsByTagName)
                    verifier = htmlElement.InnerText;
            }
            while (verifier == "");

while (www.ReadyState != WebBrowserReadyState.Complete) Application.DoEvents();