<div class="wrap">
<table>
  <tr>
    <td>test</td>
  </tr>
</table>
<table>
  <tr>
    <td>longer</td>
  </tr>
</table>
<table>
  <tr>
    <td>I'm pretty wide, really.</td>
  </tr>
</table>
  <table>
  <tr>
    <td>Lorem ipsum dolor sit amet, consectetur adipisicing elit. Nulla provident modi aut debitis minus temporibus tempore saepe quas hic ratione itaque quo quisquam earum.</td>
  </tr>
</table>
</div>

body {
  background: #ccc;
}
.wrap {
  width: 300px;
  margin: 0 auto;
  background: white;
}
table {
  border: 1px solid red;
  margin: 5px 0;
}