function $_(element)
{
	return document.getElementById(element);
}

function displayMenu(link_element)
{
	$_(link_element).style.display = '';
}

function is_child_of(parent, child)
{
	if (child != null)
	{			
		while (child.parentNode)
		{
			if ((child = child.parentNode) == parent )
				return true;
		}
	}
	return false;
}

function hideMenu(element, event, menu)
{
	var current_mouse_target = null;
	
	if (event.toElement)
		current_mouse_target = event.toElement;
	else if( event.relatedTarget )
		current_mouse_target = event.relatedTarget;

	if (!is_child_of(element, current_mouse_target) && element != current_mouse_target)
		if (current_mouse_target && current_mouse_target.id != menu)
			element.style.display = "none";
}