function toggleSitemap(duration)
{
	var sitemap_node	= $('sitemap');
	var duration		= duration ? duration : 500;
	var effect			= new Fx.Slide(sitemap_node, {duration: duration});
	var is_hidden		= sitemap_node.getStyle('visibility') == 'hidden' ? true : false;
	
	effect.toggle().chain(function()
	{
		if (is_hidden) sitemap_node.setStyle('visibility', 'visible');
	});
}