function ChangeMenuItem(num) {
  
           var divek = document.getElementById('menu'+num);
           
           divek.src = './images/menu'+num+'_on.jpg';
  }
  
  function ChangeMenuItemBack(num) {
  
           var divek = document.getElementById('menu'+num);
           
           divek.src = './images/menu'+num+'_off.jpg';
  }

  function ChangeSubMenuItem(num, pic) {
  
           var divek = document.getElementById('submenu'+num);
           
           divek.src = './images/'+pic;
  }
  
  function ChangeSubMenuItemBack(num, pic) {
  
           var divek = document.getElementById('submenu'+num);
           
           divek.src = './images/'+pic;
  }

function check_validEmail(m){
  var mail = "^[_a-zA-Z0-9\.\-]+@[_a-zA-Z0-9\.\-]+[\.]{1}[a-zA-Z]{2,4}$";
  return (m.match(mail)) ? true : false;
}