純css寫網格

  background-image: linear-gradient(90deg, #dfdfdf 2px, transparent 0), linear-gradient(#dfdfdf 2px, transparent 0), linear-gradient(90deg, #dfdfdf 1px, transparent 0), linear-gradient(#dfdfdf 1px, transparent 0)
  background-size: 100px 100px, 100px 100px, 40px 40px, 40px 40px
  background-color: #f3f3f3
  width: 100%
  height: 100%