$(function(){
		$('.ad_b').click(function(){
			var win=$("#ad_box");
			win.show();
			var width=win.width();
			var height=win.height();
			win.hide();
			win.css({
					left:$(window).scrollLeft() + ($(window).width() - width) / 2,
					top: $(window).scrollTop() + ($(window).height() - height) / 2
				}).fadeIn(500);
			});
		$("#close").live("click", function(){
			$("#ad_box").fadeOut(500);	
			});
	});