$(document).ready(function() {
	$(".nav_container_hidden").hide();
	$(".nav_container").hover(
		function () {
			$(this).children(".nav_container_hidden").slideDown("fast");
			$(this).children("a:first-child").toggleClass("nav_active");
		}, 
		function () {
			$(this).children(".nav_container_hidden").stop();
			$(this).children(".nav_container_hidden").slideUp("fast", function() {
				$(this).css({height: "auto"});
			});
			$(this).children("a:first-child").toggleClass("nav_active");
		}
	);
});