<!-- 弹出层部分 -->
<div id="box">
    <span id="closeBtn" style="color:white">关闭</span>  
<a id="gameMerry" href="http://gamemake.org/html5_game/shengdan/">挑战一下</a>
</div>

/*弹出层部分*/
#box {display: none;position: absolute;width: 440px;height: 284px;background: url(../images/layer.jpg) no-repeat;z-index: 200;
}
#closeBtn {position: absolute;right: 10px;top: 10px;cursor: pointer;color: #000	;
}
#greybackground {background: #000;display: block;z-index: 100;width: 100%;position: absolute;top: 0;left: 0;
}
#box p {position: absolute;left: 180px;bottom: 40px;}
#box p a {color: #fff;font-size: 16px;text-decoration: underline;}
#box p a:hover {text-decoration: none;}

$(function(){
　　var screenwidth,screenheight,mytop,getPosLeft,getPosTop;
　　screenwidth = $(window).width();
　　screenheight = $(window).height();
　　mytop = $(document).scrollTop();
　　getPosLeft = screenwidth/2 - 220;
　　getPosTop = screenheight/2 - 142;
　　$("#box").css({"left":getPosLeft,"top":getPosTop});   
    $(window).resize(function(){
    　　screenwidth = $(window).width();
    　　screenheight = $(window).height();
    　　mytop = $(document).scrollTop();
    　　getPosLeft = screenwidth/2 - 220;
    　　getPosTop = screenheight/2 - 142;
    　　$("#box").css({"left":getPosLeft,"top":getPosTop+mytop});
    });    
  　　$(window).scroll(function(){
    　　screenwidth = $(window).width();
    　　screenheight = $(window).height();
    　　mytop = $(document).scrollTop();
    　　getPosLeft = screenwidth/2 - 220;
    　　getPosTop = screenheight/2 - 142;
    　　$("#box").css({"left":getPosLeft,"top":getPosTop+mytop});
  　　});    
  　　
    　　$("#box").fadeIn("fast");
    　　$("body").append("
<div id="greybackground"></div>
");
    　　var documentheight = $(document).height();
    　　$("#greybackground").css({"opacity":"0.5","height":documentheight});        
  　　$("#closeBtn").click(function() {
    　　$("#box").hide();
    　　$("#greybackground").remove();
    　　return false;
  　　});
});