.cell {
  border: 1px solid red;
}

.grid {
  border: 1px solid blue;
}


.container {
  max-width: 960px;
  margin: 0 auto;
}

body, html {
  margin: 0;
  padding: 0;
}

body {
  padding: 20px;
}

* {
  box-sizing: border-box;
}