The background floor disappears at float left why?

Question

css

when I write float left the background floor disappears

<div class="footer-block footer-info">
  <div class="block-inner">
  </div>
</div>

footer {
    background: #262626;
    padding:50px 0px;
    color: #777;
    font-size: 18px;
}

.footer-block {
    width:33%;
    float:left;
}

.block-inner {
    padding:0px 15px;
}

Answer 1

Did not clear the parent container
habrahabr.ru/post/48383