$(function() {
		$(window).scroll(function() {
			var scroTop = $(window).scrollTop();
			if (scroTop > 500) {
				$('.return_top').fadeIn(500);
			} else {
				$('.return_top').fadeOut(500);
			}
		});
		$('.return_top').click(function() {
			$("html,body").animate({
				scrollTop: 0
			}, "fast");
		});
	});

	function search(s) {
		if (s == "") {
			alert("请输入关键词搜索");
			return;
		}
		location.href = "/lookup/" + s;
	}