body{/*ギザギザ(線/疎)の背景*/
background-color:#ccf;background-size:20px 20px;
background-image:
linear-gradient(-135deg,transparent 10%,#fff 10%,#fff 15%,transparent 15%),
linear-gradient(135deg,transparent 10%,#fff 10%,#fff 15%,transparent 15%),
linear-gradient(-45deg,transparent 10%,#fff 10%,#fff 15%,transparent 15%),
linear-gradient(45deg,transparent 10%,#fff 10%,#fff 15%,transparent 15%);
background-position:
10px 0px,10px 0px,0px 0px,0px 0px;
}