JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//maxcdn.bootstrapcdn.com/font-awesome/4.2.0/css/font-awesome.min.css">
<div id="opick">
  <div id="header">
    <h1>OPICK WEBLOG</h1></br>
    <p>Cara Membuat Auto Pop up Hanya Dengan CSS</div>
  <div id="menu"></div>

  <div id="content">
    <div id="main">
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
      <div id="box"></div>
    </div>
    <div id="side">
      <div id="sidecontent2" class="cf"><span>Widget 1</span></div>
      <div id="sidecontent2" class="cf"><span>Widget 2</span></div>
      <div id="sidecontent2" class="cf"><span>Widget 3</span></div>
    </div>
  </div>
  <div id="footer" class="cf"></div>
  <div id="credit"><span>by. Opick Weblog All Right Reserved</span></div>
</div>

<div class="popup-wrapper" id="popup">
<div class="popup-container">
<!-- Konten popup, silahkan ganti sesuai kebutuhan -->

<img src="https://2.bp.blogspot.com/-cKa7bYLYEag/VwyWDcUPFmI/AAAAAAAAAYc/r1U4EqKxFiw4JdCkXhKHfT4l5Lzw6P5GgCLcB/s1600/pop%2Bup.PNG">

<!-- Konten popup sampai disini-->
<a class="popup-close" href="#popup">X</a>
</div>
</div>

CSS

@import url(http://fonts.googleapis.com/css?family=Quicksand);
body {
  margin: 0;
  padding: 0;
  background: #e6e6e6;
  font-family: Quicksand, sans-serif;
}

#opick {
  margin: 5% auto;
  width: 100%;
  max-width: 920px;
  box-shadow: 0 0 0 20px rgba(0,0,0,0.03);
}

#header {
  height: 200px;
  margin: 0;
  background: #fdfdfd;
}

#header h1 {
  display: table;
  color: #999;
  font-weight: 400;
  text-align: center;
  margin: auto;
  padding: 50px 50px 0 50px;
  font-size: 55px;
}

#header p {
  display: table;
  color: #999;
  font-weight: 400;
  text-align: center;
  margin: auto;
  padding: 10px;
  font-size: 20px;
}

#menu {
  position: relative;
  height: 60px;
  margin: 0;
  background: #444;
}

#menu:before {
  position: absolute;
  content: '';
  display: inline-block;
  left: 0;
  top: 0;
  height: 60px;
  width: 80px;
  margin: 0;
  text-align: center;
  background: #efb16f;
}

#menu:after {
  position: absolute;
  content: '\f015';
  display: inline-block;
  font-family: FontAwesome;
  left: 0;
  top: 0;
  height: 60px;
  line-height: 60px;
  width: 80px;
  margin: 0;
  text-align: center;
  color: #fff;
  font-size: 20px;
}

#content {
  position: relative;
  width: 100%;
  height: 1850px;
  margin: 0;
  background: #fff;
  padding: 20px 0;
}

#main {
  position: relative;
  float: left;
  width: 70%;
  background: #fff;
}

#box {
  position: relative;
  width: 93.5%;
  height: 150px;
  display: block;
  background: #f6f6f6;
  margin: 0 20px 20px 20px;
}

#box:before {
  position: absolute;
  content: '';
  display: inline-block;
  left: 0;
  top: 0;
  height: 150px;
  width: 200px;
  margin: 0;
  background: #e6e6e6;
}

#box:after {
  position: absolute;
  content: '\f03e';
  font-family: FontAwesome;
  display: inline-block;
  left: 0;
  right: 0;
  top: 0;
  text-align: center;
  height: 150px;
  line-height: 150px;
  width: 200px;
  margin: 0;
  color: #bbb;
  font-size: 50px;
}

#side {
  background: #fff;
  width: 30%;
  float: right;
 ...