Блог iZerO.Ru

private void button1_Click(object sender, EventArgs e)
{
    NetworkCredentials nc = new NetworkCredentials("Login", "Password", "http://www.izero.ru");  
    WebClient client = new WebClient();

    client.Credentials = nc;
    String htmlCode = client.DownloadString("http://www.izero.ru/file.jpg");

    MessageBox.Show(htmlCode);
}