CSS实现 全屏 遮罩

遮罩 CSS:

.divBG 
{ 
    background: gray; 
    position: fixed; 
    left: 0px; 
    top: 0px; 
    width: 100%; 
    height: 100%; 
    display: none; 
    z-index: 20; 
    filter: alpha(opacity=60); 
    opacity: 0.5 !important; 
}

弹出层 CSS:

.PopUp 
{ 
    position: fixed; 
    display: none; 
    z-index: 50 !important; 
    background-color: White; 
    width: 900px; 
    border-style: solid solid solid solid; 
    border-width: 5px 5px 5px 5px; 
    border-color: #cccc99; 
    left: 50%; 
    top: 50%; 
    margin-top: -200px; /*--高度的一半--*/ 
    margin-left: -450px; /*--宽度的一半--*/ 
}