var main_nav_links;

function init_main_nav() {
  main_nav_links = document.getElementById('main_nav').getElementsByTagName('a');
  if(no_activate_main_link != 0) main_nav_links[0].onmouseover = activate_main_nav_links0;
  if(no_activate_main_link != 0) main_nav_links[0].onmouseout = inactivate_main_nav_links0;
  if(no_activate_main_link != 1) main_nav_links[1].onmouseover = activate_main_nav_links1;
  if(no_activate_main_link != 1) main_nav_links[1].onmouseout = inactivate_main_nav_links1;
  if(no_activate_main_link != 2) main_nav_links[2].onmouseover = activate_main_nav_links2;
  if(no_activate_main_link != 2) main_nav_links[2].onmouseout = inactivate_main_nav_links2;
  if(no_activate_main_link != 3) main_nav_links[3].onmouseover = activate_main_nav_links3;
  if(no_activate_main_link != 3) main_nav_links[3].onmouseout = inactivate_main_nav_links3;
  
  if(no_activate_main_link == 0) activate_main_nav_links0();
  if(no_activate_main_link == 1) activate_main_nav_links1();
  if(no_activate_main_link == 2) activate_main_nav_links2();
  if(no_activate_main_link == 3) activate_main_nav_links3();
  }

function activate_main_nav_links0() {
  main_nav_links[0].style.background = "url('images/main_nav_profile_hover.jpg')";
  }
  
function activate_main_nav_links1() {
  main_nav_links[1].style.background = "url('images/main_nav_operation_hover.jpg')";
  }
  
function activate_main_nav_links2() {
  main_nav_links[2].style.background = "url('images/main_nav_advantages_hover.jpg')";
  }
  
function activate_main_nav_links3() {
  main_nav_links[3].style.background = "url('images/main_nav_contact_hover.jpg')";
  }

function inactivate_main_nav_links0() {
  main_nav_links[0].style.background = "url('images/main_nav_profile.jpg')";
  }
  
function inactivate_main_nav_links1() {
  main_nav_links[1].style.background = "url('images/main_nav_operation.jpg')";
  }
  
function inactivate_main_nav_links2() {
  main_nav_links[2].style.background = "url('images/main_nav_advantages.jpg')";
  }
  
function inactivate_main_nav_links3() {
  main_nav_links[3].style.background = "url('images/main_nav_contact.jpg')";
  }