function changeMenuClass(menuCurrent, menu1, menu2, menu3, menu4, menu5, menu6)
{
  parent.document.getElementById(menuCurrent).className = 'nav_button_current'
  parent.document.getElementById(menu1).className = 'nav_button';
  parent.document.getElementById(menu2).className = 'nav_button';
  parent.document.getElementById(menu3).className = 'nav_button';
  parent.document.getElementById(menu4).className = 'nav_button';
  parent.document.getElementById(menu5).className = 'nav_button';
  parent.document.getElementById(menu6).className = 'nav_button';
}