body {
    background: 
        linear-gradient(45deg, #f0f2f5 25%, transparent 25%),
        linear-gradient(-45deg, #f0f2f5 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, #f0f2f5 75%),
        linear-gradient(-45deg, transparent 75%, #f0f2f5 75%);
    background-size: 100px 100px;
    background-position: 0 0, 0 50px, 50px -50px, -50px 0px;
    background-color: #f5f7fa;
}