function renderSubnav() 
{
	document.getElementById( "sub_nav1" ).style.display = "none";
	document.getElementById( "sub_nav2" ).style.display = "none";
	document.getElementById( "sub_nav3" ).style.display = "none";
	document.getElementById( "sub_nav4" ).style.display = "none";
}

function showSubnav(number) { document.getElementById( "sub_nav" + number ).style.display = "block"; }
function hideSubnav(number) { document.getElementById( "sub_nav" + number ).style.display = "none"; }