.returntop{
            height:85px;width:30px;background:deepskyblue;position: fixed;bottom:0;right:22px;
            text-align: center;color:white;cursor: pointer;border-radius:6px;font-size:16px;display:none;
        }
/* 设置博客正文一二三级标题格式 */
/* 一级标题 */
#cnblogs_post_body h1 {
    font-size: 28px;
    font-weight: bold;
    line-height: 1.5;
    color: black;
    margin: 10px 0;
}
/* 二级标题 */
#cnblogs_post_body h2 {
    font-size: 24px;
    font-weight: bold;
    line-height: 1.5;
    color: black;
    /* background-color: royalblue; */
    margin: 10px 0;
}
/* 三级标题 */
#cnblogs_post_body h3 {
    font-size: 20px;
    font-weight: bold;
    line-height: 1.5;
    color: black;
    /* background-color: dimgrey; */
}
/*  正文 */
#cnblogs_post_body p {
    font-size: 12pt;
}
/* adblock */
#ad_t2 {
    display: none;
}
.c_ad_block {
    display: none;
}


img {
max-width:90%;
}

body:before {
    /* background: url(https://img2020.cnblogs.com/blog/2448767/202107/2448767-20210720104654312-1204563602.jpg) center/cover no-repeat; */
    content: '';
    background-repeat: no-repeat;
    background-position: center;
    opacity: 0.3;
    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;
}
/* 定制博客背景图片，url里面是你的图片位置信息 */
/* body { 
     background-color: #efefef;
     background-image:url(https://img2020.cnblogs.com/blog/2448767/202107/2448767-20210720104654312-1204563602.jpg); 
     opacity: 0.6;
     background-repeat: no-repeat; 
     background-attachment: fixed; 
     background-position: center 0; 
     background-size: cover; 
    padding-top:0px;
  } */