body{/*斜ギンガムチェック(青系)の背景*/
background-size:20px 20px;
background-color:#def;
background-image:
linear-gradient(-45deg,rgba(0,100,255,.5) 25%,transparent 25%,transparent 50%,rgba(0,100,255,.5) 50%,rgba(0,100,255,.5) 75%,transparent 75%,transparent 100%),
linear-gradient(45deg, rgba(0,0,250,.4) 25%, transparent 25%, transparent 50%, rgba(0,0,250,.4) 50%, rgba(0,0,250,.4) 75%, transparent 75%, transparent 100%);
}