navigation_wrapper_height = document.getElementById('navigation_wrapper').offsetHeight;

document.getElementById('navigation_wrapper').onmouseover = function()
{
  // document.getElementById('nav_sub').style.height = 'auto';
  document.getElementById('nav_sub').style.overflow = 'visible';
}

document.getElementById('nav_sub').onmouseout = function()
{
  // document.getElementById('nav_sub').style.height = '246px';
  document.getElementById('nav_sub').style.overflow = 'hidden';
}