Css for grid

* { box-sizing: border-box; }

body { font-family: sans-serif; }

/ ---- grid ---- /

.grid {
  background: #EEE;
  text-align: center;
  width: 100%;
  margin: 0 auto;
  / center /
}

/ clearfix /
.grid:after {
  content: '';
  display: block;
  clear: both;
}

/ ---- grid-item ---- /

.grid-item {
  width: 33%;
  height: 120px;
  display: inline-block;
  margin: 0;
  padding: 0;
  background: #D26;
  border: 1px solid #000;
}

.grid-item--height2 { height: 200px; }
.grid-item--height3 { height: 260px; }