Выравнивание

2.5px*2 = 5px в 10 строке

by akogch

HTML

<div class="container">
  <div class="block">Content Box</div>
  <div class="block">Content Box</div>
  <div class="block">Content Box</div>
  <div class="block">Content Box</div>
  <div class="block">Content Box</div>
  <div class="block">Content Box</div>
  <div class="block">Content Box</div>
</div>

CSS

.container {
  max-width: 1000px;
  border: 1px solid #000;
  margin-top: 50px;
  margin-left: auto;
  margin-right: auto;
  overflow: hidden;
}

.block {
  width: calc(100% / 3 - 5px);
  float: left;
  margin-right: 2.5px;
  margin-left: 2.5px;
  background-color: #156;
  box-sizing: border-box;
  margin-bottom: 5px;
  height: 100px;
  text-align: center;
  line-height: 100px;
}