Edit in JSFiddle

<h2>
BLOGIT.VN
</h2>
<div class="div1">
  DIV 1
</div>
<div class="div3">
  <div class="div2">
    DIV 2
  </div>
</div>
.div1 {
  position: relative;
  z-index: 1;
  background-color: #f00;
  left: 50px;
  top: 50px;
  width: 200px;
  height: 200px;
}

.div2 {
  position: fixed;
  z-index: 2;
  background-color: #0f0;
  left: 100px;
  top: -100px;
  width: 200px;
  height: 200px;
}

.div3{
  position: relative;
  width: 300px;
  height: 300px;
  background-color: #00f;
}