JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/twitter-bootstrap/2.3.1/css/bootstrap-combined.min.css">
<div class="row row-fix">
   <div class="span5">span5</div>
   <div class="span3">span3</div>
   <div class="span2 two-col">      
         <div class="col1">span2</div>
         <div class="col2">span2</div>     
   </div>
   <div class="span2">span2</div>
</div>

<div class="row row-fix">
   <div class="span6 two-col">      
         <div class="col1">span6</div>
         <div class="col2">span6</div>     
   </div>
   <div class="span6">span6</div>
   
</div>

CSS

.row-fix { margin-bottom:20px;}

.row-fix > [class*="span"]{ height:100px; background:#f1f1f1;}

.row-fix .two-col{ background:none;}

.two-col > [class*="col"]{ height:40px; background:#ccc;}

.two-col > .col1{margin-bottom:20px;}