SOURCE

<div class="box">
    <div class="section"></div>
    <div class="footer"></div>
  </div>

 *{
      margin:0;padding:0;
    }
    body,html{
      height:100%;
    }
    .box{
      min-height:100%;
      position:relative;
    }
    .section{
      padding-bottom:50px;
      height:200px;
      background:#ccc;
   }
    .footer{
      height:50px;
      background:#333;
     position:absolute;
      bottom:0;
      width:100%;
    }