body {
    background-color: white;
    background-image: linear-gradient(45deg, black 25%, transparent 25%, transparent 75%, black 75%, black), 
    linear-gradient(45deg, black 25%, transparent 25%, transparent 75%, black 75%, black);
    background-size: 100px 100px;
    background-position: 0 0, 50px 50px;
}