CodePen

HTML

            
              <div class="page-wrap">
  
  <section class="main-content">
    <h1>Main Content</h1>
    <p><strong>I'm first in the source order.</strong></p>
    <p>The key to victory is discipline, and that means a well made bed. You will practice until you can make your bed in your sleep. Fry, we have a crate to deliver. Hey, guess what you're accessories to.</p>
    <p>I'll get my kit! That's not soon enough! Oh, all right, I am. But if anything happens to me, tell them I died robbing some old man.</p>
  </section>
  
  <nav class="main-nav">
    <h2>Nav</h2>
    <ul>
      <li><a href="#">Home</a></li>
      <li><a href="#">About</a></li>
      <li><a href="#">Clients</a></li>
      <li><a href="#">Contact Us</a></li>
    </ul>
  </nav>
  
  <aside class="main-sidebar">
    <h2>Sidebar</h2>
    <p>I am a rather effortless column of equal height.</p>
  </aside>
    
</div>
            
          
!

↑ Insert the most common viewport meta tag

CSS

            
              /* Mixins */
@mixin flexbox-display-flex
  display: -webkit-box
  display: -moz-box
  display: -ms-flexbox
  display: -webkit-flex
  display: flex

@mixin flexbox-flex($width)
  -webkit-box-flex: 1
  -moz-box-flex: 1
  width: $width
  -webkit-flex: 1
  -ms-flex: 1
  flex: 1

@mixin flexbox-order($order)
  -webkit-box-ordinal-group: $order
  -moz-box-ordinal-group: $order
  -ms-flex-order: $order
  -webkit-order: $order
  order: $order

/* Example */
.page-wrap
  +flexbox-display-flex

.main-content
  +flexbox-order(2)
  width: 60%
  -moz-box-flex: 1
  background: white

.main-nav
  +flexbox-order(1)
  +flexbox-flex(20%)
  background: #ccc

.main-sidebar
  +flexbox-order(3)
  +flexbox-flex(20%)  
  background: #ccc

/* Extra styling stuff */
.main-content,
.main-sidebar,
.main-nav
  padding: 1em

body
  padding: 2em
  background: #79a693

*
  -webkit-box-sizing: border-box
  -moz-box-sizing: border-box
  box-sizing: border-box

h1, h2
  font: bold 2em Sans-Serif
  margin: 0 0 1em 0

h2
  font-size: 1.5em

p
  margin: 0 0 1em 0
            
          
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JS

            
              /* 
Browser support

Chrome any
Firefox any
Safari any
Opera 12.1+
IE 10+

iOS any
Android any
*/
            
          
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