.err-page .err-bg {
    position: fixed;
    height: 200rem / $pxConvertRem;
    width: 200rem / $pxConvertRem;
    top: 50%;
    left: 50%;
    margin-left: -100rem / $pxConvertRem;
    margin-top: -100rem / $pxConvertRem;
    background: image-url('404.png') no-repeat;
    background-size: 100% 100%;
}