/* 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://pealfrog.gitee.io/images/picture/049.png); 
     background-repeat: no-repeat; 
     background-attachment: fixed; 
     background-position: center 0; 
     background-size: cover; 
    padding-top:0px;
  }
#topics,#mainContent,#comment_form_container,#ad_t2, .under-post-card,.c_ad_block, .under-post-card,#myposts .PostList{
    background:rgba(255,255,255,0.5);
}