lastNavLayer = null;
numSubs = 3;

function toggleNav(layer)
{
  var navLayer = document.getElementById(layer);

  if (lastNavLayer != null && navLayer != lastNavLayer && lastNavLayer.style.display == "block")
  	lastNavLayer.style.display = "none";

  if (!navLayer.style.display || navLayer.style.display == "none")
  	navLayer.style.display = "block";
  else
  	navLayer.style.display = "none";
  lastNavLayer = navLayer;
}

function hideSubNav()
{
	for (i=1; i<=numSubs; i++)
	{
		var navLayer = document.getElementById("subNav" + i);
		navLayer.style.display = "none";
	}
}

var oldhandler = window.onload;
window.onload = (typeof oldhandler == "function")
    ? function() { oldhandler(); hideSubNav(); } : hideSubNav;