I try to change a link use the webBrowser1

I try to change a link use the webBrowser1 after authorization but the webBrowser1 opens the start site

private void button1_Click(object sender, EventArgs e)
        {


            webBrowser1.Navigate("http://server/application/login/");
            pause_wb();
            webBrowser1.Document.GetElementById("username").InnerText = "user1";
            pause_wb();             
            webBrowser1.Document.GetElementById("password").SetAttribute("value", "pass1");
            pause_wb();

            webBrowser1.Document.GetElementById("userSignIn").InvokeMember("click");
            pause_wb();

            webBrowser1.Navigate("http://server/application/obj/");
         }

Pause for loads

        public void pause_wb()
        {
            while (webBrowser1.ReadyState != WebBrowserReadyState.Complete)
            {
                Application.DoEvents();
            }
        }

If run the programm after the string webBrowser1.Navigate("http://server/application/obj/"); webBrowser1 goes to start the site http://server/application/login/

How can i change a link and save authorization?