CodePen

HTML

            
              <div class="navigation">
  Navigation
</div>

<div class="blue-box">
 Blue box
</div>

<div class="left-column">
  <div class="dark-grey-text">
  Dark grey text: Fusce tincidunt, libero at luctus malesuada, lorem odio pellentesque justo, quis vulputate sem arcu sit amet orci. Nulla mollis mattis urna, ut molestie tellus viverra eu. Vivamus sed ullamcorper justo. Vivamus bibendum sapien in leo malesuada pulvinar. Quisque iaculis aliquam ornare. In ante erat, elementum sed est sed, sollicitudin tincidunt mauris. Nulla at porttitor lorem. Quisque magna tortor, sollicitudin ut convallis quis, faucibus vitae diam. In vitae leo risus. Nulla nec eros id quam malesuada pharetra.
  </div>
  <div class="grey-text">
  Grey text: Lorem ipsum dolor sit amet, consectetur adipiscing elit. Nullam sed nulla ultricies, cursus est ut, facilisis felis. Maecenas sit amet porttitor ipsum, vitae viverra augue. Nunc condimentum lobortis purus, non facilisis magna facilisis sit amet. Mauris gravida ultrices arcu, non vestibulum nisi eleifend eu. Donec eleifend risus turpis, eu vehicula velit iaculis nec. Proin mollis, erat ac pellentesque viverra, lacus lectus faucibus sem, vitae vestibulum turpis nunc et metus. Sed consectetur tellus viverra, feugiat magna nec, commodo metus.
  </div>
</div>

<div class="pink-green-wrapper">
<div class="green-box">
  Green box
</div>

<div class="pink-box">
  Pink box
</div>
</div>

<div class="footer">
  Footer
</div>
            
          
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↑ Insert the most common viewport meta tag

CSS

            
              .navigation {
  clear: both;
  height: 50px;
  margin-bottom: 20px;
  background-color: black;
  color: white;
}

.blue-box {
  float: right;
  width: 20%;
  height: 150px;
  margin-bottom: 20px;
  background-color: blue;
}

.left-column {
  float: left;
  width: 75%;
}
.dark-grey-text {
  
}

.grey-text {
  margin-top: 20px;
  margin-bottom: 20px;
  color: grey;
}

.pink-green-wrapper {
  width: 20%;
  float:right;
  clear: right;
  margin-bottom: 20px;
}

.pink-box {
  float: left;
  width: 50%;
  height: 150px;
  background-color: pink;
}

.green-box {
  float: left;
  width: 50%;
  height: 150px;
  background-color: green;
}



.footer {
  clear: both;
  height: 50px;
  background-color: black;
  color: white;
}

@media all and (max-width: 480px)  {
		.blue-box {
		  float: none;
			width: 100%;
		}
    .left-column {
      width: 100%;
      float: none;
    }
          .pink-green-wrapper {
            float: none;
            width: 100%;
          }
    .pink-box, .green-box {
      float: left;
      width: 50%;
      margin-bottom: 20px;
    }
}
            
          
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