.err-page {
    .err-bg {
        position: fixed;
        height: 200px;
        width: 200px;
        top: 50%;
        left: 50%;
        margin-left: -100px;
        margin-top: -100px;
        background: resolve("common/404.png") no-repeat;
        background-size: 100% 100%;
    }
}