.layer {display:none; position:fixed; position:absolute; top:0; left:0; width:100%; height:100%; z-index:10000;}
.open {display:block;}
.layer .bg {position:absolute; top:0; left:0; width:100%; height:1000%; background:#000; opacity:.85; filter:alpha(opacity=50);}

.layer_area {position:absolute; left:50%; top:50%; background:#fff; padding:20px; border:4px solid #ddd; border-radius: 10px;}