DIV弹出层，可以模仿框架来实现

在ie6下会出现问题，将宽度和高度设置如下：

.black_overlay{
            display: none;
            position: absolute;
            top: 0%;
            left: 0%;
            width: expression(document.body.clientWidth) ;
     height: expression(document.body.clientHeight) ;
            background-color: gray;
            z-index:1001;
            -moz-opacity: 0.8;
            opacity:.80;
            filter: alpha(opacity=80);
}

即可解决