js css implements mask centered pop-up layer (scrolls with the browser window scroll bar)_javascript skills

< ;style type="text/css">
*{}{margin:0;padding:0;}
html{}{_background:url(about:blank);} /**//* Prevent flashing in IE6, replace empty files with about:blank, reduce requests */
body{}{background:#fff; font: 12px/1.5 Tahoma,Geneva, \5b8b\4f53, sans-serif; height:100%;}
.wrap{}{height:980px; padding-top:20px;text-align:center;}
p{}{font-size:14px;text-align:center;line-height:24px;}
/**//** Mask layer **/
#masklayer{}{
background:#000;
display:none;
filter:alpha(opacity = 50);
opacity:0.5;
top:0;
left:0;
height:100%;
width:100%;
z-index:999;
position:fixed;
_position:absolute;
_left: expression(documentElement.scrollLeft documentElement.clientWidth - this.offsetWidth);
_top: expression(documentElement.scrollTop documentElement.clientHeight - this.offsetHeight);
}
/**//** Popup layer **/
#popup{}{
display:none;
width:300px;
z-index:1000;
left:50%;
top:50%;
position: fixed!important;
margin-left:-150px !important;
_position:absolute;
_top:expression(eval(document.compatMode && document.compatMode=='CSS1Compat')?
documentElement .scrollTop (document.documentElement.clientHeight - this.offsetHeight)/2: /**//*IE6*/
document.body.scrollTop (document.body.clientHeight - this.clientHeight)/2); /** //*IE5 IE5.5*/
}
.content{}{background:#f3f3f3;border:1px solid #999;}
.content h3{}{background:#a0a0a0;color:#fff;font -size:14px;height:32px;line-height:32px; padding-left:5px;}
#clickbtn{}{margin-top:20px;}

< /head>



< div id="popup">