body:before {
    background: url(https://img2020.cnblogs.com/blog/2424554/202107/2424554-20210713203702702-103116016.png) center/cover no-repeat;
    content: '';
    background-repeat: no-repeat;
    background-position: center;
    opacity: 0;
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: -1;
    -webkit-filter: grayscale(40%);
    -moz-filter: grayscale(40%);
    -ms-filter: grayscale(40%);
    -o-filter: grayscale(40%);
    filter: grayscale(40%);
    filter: gray;
}
a#cb_post_title_url{
    color: red;
    font-size: 30px;
}