<div class="contents clearfix">
  <div class="post"></div>
  <div class="post"></div>
  <div class="post"></div>
  <div class="post"></div>
</div>
* {
  -webkit-box-sizing: border-box;
  -moz-box-sizing: border-box;
  box-sizing: border-box;
  font-family: 'Raleway', sans-serif;
}

.clearfix:after {
  content: "";
  clear: both;
  display: block;
}

.contents {
  margin: 0 auto;
  width: 400px;
}

.post {
  background: #8DCF3F;
  float: left;
  height: 200px;
  opacity: 0;
  width: 50%;
}

.post:nth-child(3n+1) {
  background: #F58E7E;
}
$(function() {
  $(window).load(function() {
    var fadeSpeed = 1000;
    $('.post').each(function(i) {
      $(this).delay(i * 500).animate({
        'opacity': 1
      }, fadeSpeed);
    });
  });
});

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. //cdnjs.cloudflare.com/ajax/libs/jquery/2.1.3/jquery.min.js
  2. //cdnjs.cloudflare.com/ajax/libs/jqueryui/1.11.2/jquery-ui.min.js