body {
background-color: #eee;
background-image: linear-gradient(45deg, #000 25%, transparent 25%, transparent 75%, #000 75%, #000),
linear-gradient(45deg, #000 25%, transparent 25%, transparent 75%, #000 75%, #000);
background-size:60px 60px;
background-position:0 0, 30px 30px
}