body{/*メッシュ(黒)の背景*/
background-size:30px 30px;
background-color:#fff;
background-image:
linear-gradient(90deg,transparent 25px,#000 0),
linear-gradient(180deg,transparent 25px,#000 0),
linear-gradient(90deg,transparent 20px,#333 0),
linear-gradient(180deg,transparent 20px,#333 0),
linear-gradient(90deg,transparent 15px,#666 0),
linear-gradient(180deg,transparent 15px,#666 0),
linear-gradient(90deg,transparent 10px,#999 0),
linear-gradient(180deg,transparent 10px,#999 0),
linear-gradient(90deg,transparent 5px,#ccc 0),
linear-gradient(180deg,transparent 5px,#ccc 0);
}