.maskHistory {
     position: fixed;
    left: 0;
    top: 0;
    z-index: 241;
    width: 100%;
    height: 100%;
    background-color: #000;
    opacity:0.6;
    filter:alpha(opacity=60);
    -ms-filter: "progid:DXImageTransform.Microsoft.Alpha(opacity=60);"; 
}
.center {
    text-align: center;
    font-size: 16px;
    padding-top: 10px;
    padding-bottom: 50px;
}