var timeout	= 500;
var closetimer	= 0;
var active_menu	= 0;

function open_dd_menu(id)
{	
	// cancel close timer
	dd_cancel_close_time();

	// close old layer
	if(active_menu) active_menu.style.visibility = 'hidden';

	// get new layer and show it
	active_menu = document.getElementById(id);
	active_menu.style.visibility = 'visible';

}
// close showed layer
function close_dd_menu()
{
	if(active_menu) active_menu.style.visibility = 'hidden';
}

// go close timer
function dd_close_time()
{
	closetimer = window.setTimeout(close_dd_menu, timeout);
}

// cancel close timer
function dd_cancel_close_time()
{
	if(closetimer)
	{
		window.clearTimeout(closetimer);
		closetimer = null;
	}
}

document.onclick = close_dd_menu;