js弹层问题，急。。。
在火狐浏览器不兼容，遮罩层没有透明度。

JScript code

<style type="text/css">        #massage_box        {            position: absolute;            z-index:9999;            top: 50%;            left: 50%;            width: 400px;            height: 200px;            background: #fff;            margin: -102px 0 0 -202px;            display: none;        }        #mask        {            background-color: #666666;            z-index:1;            position: absolute;            width:1024px;            height:1000px;            opacity=0.5;             display: none;            filter: alpha(opacity=50);            -moz-opacity: 0.5;        }        .massage        {            border: #036 solid;            border-width: 1 1 3 1;            width: 95%;            height: 95%;            background: #fff;            color: #036;            font-size: 12px;            line-height: 150%;        }        .header        {            background: #036;            height: 10%;            font-family: Verdana, Arial, Helvetica, sans-serif;            font-size: 12px;            padding: 0 0 0 0;            color: #fff;        }        .font        {            font-size: 14px;        }    </style>    <script type="text/javascript">        var Obj=''   document.onmouseup=MUp   document.onmousemove=MMove  function MDown(Object){       Obj=Object.id       document.all(Obj).setCapture()       pX=event.x-document.all(Obj).style.pixelLeft;       pY=event.y-document.all(Obj).style.pixelTop;   }  //鼠标移动function MMove(){       if(Obj!=''){           document.all(Obj).style.left=event.x-pX;           document.all(Obj).style.top=event.y-pY;       }   }  function MUp(){       if(Obj!=''){           document.all(Obj).releaseCapture();           Obj='';       }   }   //弹出层function d_x(){      //mask.style.width = document.body.scrollWidth + "px";      //mask.style.height = document.body.scrollHeight + "px";    //mask.style.left = (parseInt(document.body.scrollWidth) - 1024) / 2 + "px"; // 屏幕居中        mask.style.display = "block";    massage_box.style.display = "block"    ;}  //取消层function d_y(){      mask.style.display = "none";    massage_box.style.display = "none"    ;}  

[解决办法]
注意红色部分

#mask
{
background-color: #666666;
z-index:1;
position: absolute;
width:1024px;
height:1000px;
opacity:0.5;
display: none;
filter: alpha(opacity=50);
-moz-opacity: 0.5;
}
[解决办法]
属性啊 opacity在标准浏览器中可以实现透明，如果是IE就可以使用filter
[解决办法]
把-moz-opacity去掉，ff下只要使用opacity:0.5就行了，前面那个已经无效了