Gridlines background

gridlines.css

body {
  min-height: 100vh;
  background-image:
    linear-gradient(to right, #555, transparent 1px, transparent 9px),
    linear-gradient(to bottom, #555, transparent 1px, transparent 9px),
    linear-gradient(to right, #ccc, transparent 1px, transparent 9px),
    linear-gradient(to bottom, #ccc, transparent 1px, transparent 9px);
  background-repeat: repeat;
  background-size:
    100px 100px,
    100px 100px,
    10px 10px,
    10px 10px;
  padding: 0;
  margin: 0;
}