body{/*千鳥格子*/
background-color:#bdf;
background-image:
linear-gradient(-45deg,#fff 25%,transparent 25%,transparent 75%,#bdf 75%),
linear-gradient(135deg,#fff 25%,transparent 25%,transparent 75%,#bdf 75%),
linear-gradient(-45deg,#fff 12.5%,transparent 12.5%,transparent 25%,#fff 25%,#fff 37.5%,transparent 37.5%,transparent 62.5%,#fff 62.5%,#fff 75%,transparent 75%,transparent 87.5%,#fff 87.5%);
background-size:20px 20px;
background-position:0 10px,10px 0,0 0;
}