.gray{ width: 100%; height: 100%; background-color: rgba(0,0,0,.4);position: fixed;z-index: 99; display: none;filter:progid:DXImageTransform.Microsoft.gradient(startColorstr=#7f000000,endColorstr=#7f000000);top:0;left: 0; }原文：http://www.cnblogs.com/mtuitui/p/5084665.html