Problem to add background using Skeleton Grid

Question

I'm new on programing and I'm studying HTML and CSS. But today I have a issue that I can't figure how to solve: I'm trying to add a background to a footer and it work pretty nice. But when I add "columns class" in some 'divs' it jusp stop works.

I'm adding two JS, first one whitout columns' class and a seccond one whit columns' class. I know I'm doing something wrong, but I can't figure what.

First Code whit background working perfectly

Seccond Code whit background does't work

And I'm puting here my HTML code:

<footer>
<div class="footer">
  <div class="container">
    <div class="six columns">
      <h3>Nossa História</h3>
      <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.</p>
    </div>


    <div class="three columns">
      <h3>Contato</h3>
      <ul>
        <li>- 38 99999-9999</li>
        <li>- [email protected]</li>
        <li>- Salinas - MG</li>
      </ul>
    </div>

    <div class="three columns">
      <h3>Redes Sociais</h3>
      <ul>
        <li><a href="http://facebook.com" target="_blank"><img src="img/facebook-icone.svg" alt="Ícone Facebook"></a></li>
        <li><a href="http://instagram.com" target="_blank"><img src="img/instagram-icone.svg" alt="Ícone Instagram"></a></li>
        <li><a href="http://youtube.com" target="_blank"><img src="img/youtube-icone.svg" alt="Ícone Youtube"></a></li>
      </ul>
    </div>
  </div>
</div>
</footer>

And my CSS code:

.footer {
color: #fefefd;
background: #191f28;
}