var displayed = null;

var LINK = "_link";

(function()
{
  if (window.addEventListener)
  {
    window.addEventListener("load", setup_drop_down_menu, false);    
  }
  else
  {
    window.attachEvent("onload", setup_drop_down_menu);
  }
})();

function setup_drop_down_menu()
{
  //var divs = document.getElementById("navigation_menu").getElementsByTagName("div");
  var div1 = document.getElementById("menu_2");
  setup_link(div1.id);  
  var div2 = document.getElementById("menu_3");
  setup_link(div2.id);
  var div3 = document.getElementById("menu_4");
  setup_link(div3.id);
 // for (var i = 0; i < divs.length; i++)
  //{    
    //setup_link(divs[i].id);
 // }
}

function setup_link(div_id)
{
  var link = document.getElementById(div_id + LINK);
  
  link.onclick = function(){display_menu(div_id); document.currentOpenedMenu = div_id;};
  link.onmouseout = function(){hide_displayed_menu(); }
  //link.onclick = function(){hide_displayed_menu();} 
}

function hide_displayed_menu()
{
	
  if (displayed)
  {
    displayed.style.display = 'none';
    displayed = null;
  }
}

function display_menu(id)
{
  hide_displayed_menu();

  displayed = document.getElementById(id);
  displayed.style.display = 'block';
  
  displayed.onmouseover = function(){display_menu(id);};
  displayed.onmouseout = function(){hide_displayed_menu();};    
  displayed.onclick = function(){hide_displayed_menu();};
}