.z-popup-overlay{

    width:100%;

    min-height: 100%;

    height:800px;

    position: absolute;

    top:;

    left:;

    z-index:;

    background-color: #000;

    opacity: 0.5;

    filter:alpha(opacity=50);

}

.z-popup{

    position: fixed;

    top:200px;

    _position:absolute;

    _top:expression(eval(document.documentElement.scrollTop + 200));

    z-index:;

    background:#fff;

    left:50%;

    border:2px solid #de8700;

    border-radius:5px;

}

.z-popup-close{

    position: absolute;

    top:2px;

    right: 2px;

    color:#f00;

    cursor:pointer;

}

.z-popup-content{

    padding:10px;

}

(function ($) {

    /*

     * 原理：生成和移除弹出层

     * 用法：Popup(html).show();  字符串html是弹出层的主体

     *

    */

    var Z_Popup = function (html){

        // 基本结构

        var $overlay = $('<div class="z-popup-overlay"></div>'),

            $popup = $('<div class="z-popup">' +

                        '<a class="z-popup-close">X</a>' +

                        '<div class="z-popup-content">' +

                            (html ? html : '') +

                        '</div>' +

                     +'</div>');

        return {

            show: function () {

                // a singleton

                if ($(".z-popup").length !== 0) {

                    return true;

                }

                // generate popup

                $("body").append($overlay).append($popup);

                var that = this;

                $overlay.css({

                    height: $(document).height()

                });

                $popup.css({

                    "margin-left": -($popup.width() / 2) + "px"

                });

                $(".z-popup-close").on("click", function (e) {

                    e.preventDefault();

                    that.hide();

                });

            },

            hide: function () {

                // remove the popup overlay and popup

                $overlay.remove();

                $popup.remove();

            }

        };

    };

    // 用法

    Z_Popup('<p>hello</p>').show();

})(jQuery);