title: Bootstrap - padding in span makes it bigger
body: <pre><code>    &lt;div class="row"&gt;
          &lt;div id="cover" class="span12"&gt;&lt;/div&gt;
      &lt;/div&gt;
      &lt;div class="row"&gt;
          &lt;div id="first_left" class="span6 left"&gt;
              &lt;h3&gt;aa&lt;/h3&gt;
  
          &lt;/div&gt;
          &lt;div id="first_right" class="span5"&gt;
              ee
          &lt;/div&gt;
      &lt;/div&gt;
  </code></pre>
  
  <p>And less:</p>
  
  <pre><code>#cover{
      background: url('couv.jpg') no-repeat;
      width: 960px;
      height: 280px;
  }
  
  h3{
      color: #212121;
      font-size: 18px;
      font-weight: normal;
      float: left;
      text-transform: uppercase;
      margin: 0 0 25px 0;
      text-shadow: 1px 2px 2px #FFF;
  }
  
  .left{
      background: url('grille.jpg');
      padding: 15px;
  }
  </code></pre>
  
  <p>The "first_right" span displays below first_left, and only if the 15px padding is present. With padding 15, first_left becomes 490px wide instead of 460px. Why is that ?
  Also, is it ok to have padding on a span if I want to nest some more rows in it ?</p>