您可以执行与将元素向上滑动相反的操作:

You can just do the opposite of what you are doing to slide-up the element:

$('.window .close').click(function (e) {
    //Cancel the link behavior
    e.preventDefault();
    $(this).closest('.window').animate({
        marginTop : 1200,
        opacity   : 0
    }, 400, function () {
        $(this).css('display', 'none');
    });
}); 

您的代码中有一些错误:

There are a few errors in your code:

1. .animate({marginTop:'0px', opacity:'1', },400)有一个逗号结尾，将在Internet Explorer中强制错误，它应该是:.animate({marginTop:'0px', opacity:'1' },400).
2. 您在同一元素上连续两次调用.css，您只需将对象传递给.css函数，就像在代码中的进一步介绍一样:

1. .animate({marginTop:'0px', opacity:'1', },400) has a trailing comma that will force errors in Internet Explorer, it should be: .animate({marginTop:'0px', opacity:'1' },400).
2. You call .css twice in a row on the same element, you can just pass an object to the .css function like you do further down in your code:

.

$(id).css({
    top     : winH/2-$(id).height()/2,
    left    : winW/2-$(id).width()/2,
    display : 'block'
}).animate({marginTop:'0px', opacity:'1' },400);

注意，我还链接了.animate()函数调用，这样您只需选择一次$(id).

Notice I also chained the .animate() function call, this way you only select $(id) once.

您是否知道jQuery已经具有执行此操作的功能?

Are you aware that jQuery already has functions that do this?

• .slideUp(): http://api.jquery.com/slideup
• .slidedown(): http://api.jquery.com/slidedown
• .slideToggle(): http://api.jquery.com/slidetoggle

• .slideUp(): http://api.jquery.com/slideup
• .slidedown(): http://api.jquery.com/slidedown
• .slideToggle(): http://api.jquery.com/slidetoggle

这是您的jsfiddle的更新版本: http://jsfiddle.net/4hw8H/1/

Here is an updated version of your jsfiddle: http://jsfiddle.net/4hw8H/1/

$(function() { 

    $('a[name=modal]').click(function(e) {
        e.preventDefault();

        var $this      = $($(this).attr('href')),
            winH       = $(window).height(),
            winW       = $(window).width(),
            maskHeight = $(document).height(),
            maskWidth  = $(window).width();

        $('#mask').css({
            width  : maskWidth,
            height : maskHeight
        }).fadeIn(600);   

        $this.css({
            top     : winH / 2 - $this.height() / 2,
            left    : winW / 2 - $this.width() / 2,
            display : 'block'
        }).animate({
            marginTop : 0,
            opacity   : 1
        }, 400);

    });

    $('.window .close').click(function (e) {
        e.preventDefault();
        $(this).closest('.window').animate({
            marginTop : 1200,
            opacity   : 0
        }, 400, function () {
            $(this).css('display', 'none');
        });
        $('#mask').fadeOut(600);
    });    

    $('#mask').click(function () {
        $('.window .close').trigger('click');
    });        

});