body{height:100%;}div.blocking-invisible{display:none;}div.blocking-visible{display:block;position:absolute;top:0;left:0;width:100%;height:100%;text-align:center;background:#fff;opacity:.75;filter:alpha(opacity = 75);border-top:1px solid #ddd;border-bottom:1px solid #ddd;padding-top:25%;}