遮罩z-index 1040
彈窗z-index 1050
#content 絕對定位 沒設(shè)層級 #content彈窗是父子關(guān)系 遮罩和#content是兄弟關(guān)系

#content {
    -webkit-animation: fadeIn .4s;
    animation: fadeIn .4s;
    -webkit-animation-fill-mode: forwards;
    animation-fill-mode: forwards;
    /* -webkit-transition: opacity .4s;
    -o-transition: opacity .4s;
    transition: opacity .4s;
    opacity: 0; */
}

#content.fade-in {
    opacity: 1;
}

@-webkit-keyframes fadeIn {
    0% {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}

@keyframes fadeIn {
    0% {
        opacity: 0;
    }

    to {
        opacity: 1;
    }
}