<div class="container">
  <div class="row">
    <div class="col-md-9">
      Level 1: .col-md-9
      <div class="row">
        <div class="col-md-6">
          Level 2: .col-md-6
        </div>
        <div class="col-md-6">
          Level 2: .col-md-6
        </div>
      </div>
    </div>
    <div class="col-md-3">
    </div>
  </div>
</div>
[class^="col-md"] {
    padding-top: 10px;
    padding-bottom: 10px;
    background-color: #eee;
    background-color: rgba(86,61,124,.15);
    border: 1px solid #ddd;
    border: 1px solid rgba(86,61,124,.2);
}
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External CSS

  1. https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css

External JavaScript

This Pen doesn't use any external JavaScript resources.