HtmlDocument vdoc;

            vdoc = webBrowser1.Document;

            string html = vdoc.Body.InnerText.ToString();

            HtmlElementCollection inputs = webBrowser1.Document.GetElementsByTagName("input");
            HtmlElementCollection buttons = webBrowser1.Document.GetElementsByTagName("button");

                for (int i = 0; i < vdoc.Links.Count - 1; i++)
                {
                    string href = vdoc.Links[i].OuterHtml.ToString();
                    if (href.IndexOf("退出") >= 0)
                    {
                        vdoc.Links[i].InvokeMember("click");
                    }

                }

                vdoc.GetElementById("username").InnerText = yahooid;
                vdoc.GetElementById("passwd").InnerText = password;

                vdoc.GetElementById("submit").InvokeMember("click");