HtmlElement name = webBrowser1.Document.GetElementById("ctl00$content$loginname");

 if (name != null)

     name.SetAttribute("value", User);

 HtmlElement pass = webBrowser1.Document.GetElementById("ctl00$content$pwd");

 if (pass != null)

     pass.SetAttribute("value", Password);

 HtmlElement login = webBrowser1.Document.GetElementById("ctl00_content_summit");

 if (login != null)

     login.InvokeMember("click");