This code doesn't work!!!

Question

private void button1_Click(object sender, EventArgs e)
  {
  webBrowser1.Navigate("http://facebook.com");

// I WANT TO GO TO FACEBOOK DOT COM FIRST!!! AFTER, I WANT TO FILL ALL FORMS AUTOMATICALLY.

      foreach (HtmlElement element in webBrowser1.Document.All)
  {
  if (element.Name == "email")
  {
  element.InnerText = textBox1.Text;
  }
  if (element.Name == "pass")
  {
  element.InnerText = textBox2.Text;
  }

  }
  webBrowser1.Document.GetElementById("uxlqua_5").InvokeMember("click");
  }

But this code gives framenetwork error. Because my software try to fill all forms before loading facebook.com .... how can I avoid this error? I want to fill all forms when facebook.com page is loaded in webBrowser1 ...