function img_act (imgName) 
{
  document [imgName].src = "images/" + imgName + "_on.gif";
}

function img_inact (imgName) 
{
  document [imgName].src = "images/" + imgName + "_off.gif";
} 

function go_back ()
{
  window.history.back();
}

function go_top ()
{
  window.scroll (0,0);
}

function preload_on_pics ()
{
  img1 = new Image ();
  img2 = new Image ();
  img3 = new Image ();
  img4 = new Image ();
  img5 = new Image ();
  img6 = new Image ();
  img7 = new Image ();
  img8 = new Image ();
  img9 = new Image ();
  img10 = new Image ();
  img11 = new Image ();
  img12 = new Image ();
  img13 = new Image ();
  img14 = new Image ();
  img15 = new Image ();
  img16 = new Image ();
  img17 = new Image ();
  img18 = new Image ();
  img19 = new Image ();
  img20 = new Image ();
  img21 = new Image ();
  img22 = new Image ();
  img23 = new Image ();
  img1.src = "images/main_on.gif";
  img2.src = "images/about_on.gif";
  img3.src = "images/news_on.gif";
  img4.src = "images/service_on.gif";
  img5.src = "images/billing_on.gif";
  img6.src = "images/back_on.gif";
  img7.src = "images/help_on.gif";
  img8.src = "images/find_on.gif";
  img9.src = "images/top_on.gif";
  img10.src = "images/go_on.gif";
  img11.src = "images/enter_on.gif";
  img12.src = "images/back_on.gif";
  img13.src = "images/help_on.gif";
  img14.src = "images/top_on.gif";
  img15.src = "images/go_on.gif";
  img16.src = "images/enter_on.gif";
  img17.src = "images/login_on.gif";
  img18.src = "images/ch_pass_on.gif";
  img19.src = "images/exit_on.gif";
  img20.src = "images/view_bill_on.gif";
  img21.src = "images/ch_pass_button_on.gif";
  img22.src = "images/balance_on.gif";
  img23.src = "images/add_on.gif";
}