Grid With Negative Margins

HTML

<!-- 
=================================================================
Creating grids without the need to remove margin from first/last divs
================================================================

Created as a response to Chris Coyier's article:
http://css-tricks.com/dont-overthink-it-grids/#comment-187046

Thanks to @csswizardry where I originally saw this done http://csswizardry.com/inuitcss
-->
<div class="container">
  <div class="row">
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
    <div class="col"></div>
  </div>
</div>

CSS

.container 
{
  max-width: 1080px;
  width: 100%;
  margin: 0 auto;
  background: gray;
}

.row 
{
  position: relative;
  margin-left: -20px;
  padding: 0 20px;
  background: yellow;
}

.row:after
{
  content: "";
  display: block;
  clear: both;
}

.col 
{
  float: left;
  width: calc(25% - 20px);
  height: 100px;
  margin-left: 20px;
  margin-bottom: 20px;
  background: red;
}