body {
  background-color: #aaa;
  background-image: repeating-linear-gradient(
      0deg,
      transparent,
      transparent 9px,
      rgb(113, 121, 126) 10px
    ),
    repeating-linear-gradient(
      90deg,
      transparent,
      transparent 9px,
      rgb(113, 121, 126) 10px
    );
  background-size: 100px 100px;
}