Bootstrap Grid is Responsive


examples/bootstrap/responsive_grid.html
<html>
  <head>
  <title>Responsive Grid</title>
  <meta name="viewport" content="width=device-width" />
  <link href="css/bootstrap.min.css" rel="stylesheet" />

  <style>
  .left {
      background-color: red;
  }
  .main {
      background-color: lightblue;
  }
  .right {
      background-color: lightgreen;
  }
  .main-left {
      background-color: lightblue;
  }
  .main-right {
      background-color: blue;
  }
  </style>
  </head>
  <body>
    <div class="container-fluid">
      <!-- Stack the columns on mobile by making one full-width and the other half-width -->
      <div class="row">
        <div class="col-xs-12 col-md-8 main">.col-xs-12 .col-md-8</div>
        <div class="col-xs-6 col-md-4 right">.col-xs-6 .col-md-4</div>
      </div>
      <hr>

      <!-- Columns start at 50% wide on mobile and bump up to 33.3% wide on desktop -->
      <div class="row">
        <div class="col-xs-12 col-sm-6 col-md-4 left">.col-xs-12 .col-sm-6 .col-md-4</div>
        <div class="col-xs-12 col-sm-6 col-md-4 main">.col-xs-12 .col-sm-6 .col-md-4</div>
        <div class="col-xs-12 col-sm-6 col-md-4 right">.col-xs-12 .col-sm-6 .col-md-4</div>
      </div>
      <hr>
       
      <!-- Columns start at 50% wide on mobile and bump up to 33.3% wide on desktop -->
      <div class="row">
        <div class="col-xs-6 col-md-4 left">.col-xs-6 .col-md-4</div>
        <div class="col-xs-6 col-md-4 main">.col-xs-6 .col-md-4</div>
        <div class="col-xs-6 col-md-4 right">.col-xs-6 .col-md-4</div>
      </div>
      <hr>
      
      <!-- Columns are always 50% wide, on mobile and desktop -->
      <div class="row">
        <div class="col-xs-6 left">.col-xs-6</div>
        <div class="col-xs-6 right">.col-xs-6</div>
      </div>
      <hr>

      <div class="row">
        <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3 left">.col-xs-12 .col-sm-6 .col-md-4 col-lg-3</div>
        <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3 main-left">.col-xs-12 .col-sm-6 .col-md-4 col-lg-3</div>
        <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3 main-right">.col-xs-12 .col-sm-6 .col-md-4 col-lg-3</div>
        <div class="col-xs-12 col-sm-6 col-md-4 col-lg-3 right">.col-xs-12 .col-sm-6 .col-md-4 col-lg-3</div>
      </div>
      <hr>


    </div>  
  </body>
</html>