var current_nav = '';
	function nav_over(n) {
		$('nav'+n).setStyle('backgroundPosition','center -32px');
		current_nav = n;
	}
	
	function nav_out() {
		if (current_nav != '') {
			$('nav'+current_nav).setStyle('backgroundPosition','center 0px');
			current_nav = '';
		}
	}