I have a DOM structure like this:

`div#holder > table > tbody > tr > td`

I have specified the `td` to be a fixed widht of `15px`. But when I resize the `#holder`'s width, the `td`'s width changed.

I would like to know:

1. Why the given number is not ruling?
2. How can I make the `td`'s width fixed?

Thanks,

```js
setInterval(function(){
  var w = 300*Math.random();
  $('#holder').css('width', w + 'px');
},500)
```

```css
td {
width:15px;
height:50px;
background:#f00;
}
```

```html
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div id="holder">
  <table>
    <tbody>
      <tr>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
        <td></td>
      </tr>
    </tbody>
  </table>
</div>
```