title: Three grid, if one empty, expand two others
body: <p>Im using a responsive three grid layout. Lets say each is 33% width, if one grid/div is empty, I'd like other two to expand to 50% width, and if 2 grid/divs are empty, I'd like remaining one to be 100% width.
  Can it be done purely by CSS?</p>
  
  <pre><code>&lt;div class="section group"&gt;
      &lt;div class="col span_1_of_3"&gt;
      This is column 1
      &lt;/div&gt;
      &lt;div class="col span_1_of_3"&gt;
      This is column 2
      &lt;/div&gt;
      &lt;div class="col span_1_of_3"&gt;
      This is column 3
      &lt;/div&gt;
  &lt;/div&gt;
  
  
  /*  SECTIONS  */
  .section {
      clear: both;
      padding: 0px;
      margin: 0px;
  }
  
  /*  COLUMN SETUP  */
  .col {
      display: block;
      float:left;
      margin: 1% 0 1% 1.6%;
  }
  .col:first-child { margin-left: 0; }
  
  /*  GROUPING  */
  .group:before,
  .group:after { content:""; display:table; }
  .group:after { clear:both;}
  .group { zoom:1; /* For IE 6/7 */ }
  
  /*  GRID OF THREE  */
  .span_3_of_3 { width: 100%; }
  .span_2_of_3 { width: 66.13%; }
  .span_1_of_3 { width: 32.26%; }
  
  /*  GO FULL WIDTH BELOW 480 PIXELS */
  @media only screen and (max-width: 480px) {
      .col {  margin: 1% 0 1% 0%; }
      .span_3_of_3, .span_2_of_3, .span_1_of_3 { width: 100%; }
  }
  </code></pre>