Edit in JSFiddle

<h2>
BLOGIT.VN
</h2>
<div>
  <div class="header">
     HEADER
  </div>
  <div class="body">
    <div class="menu">
      MENU BAR
    </div>
    <div class="content">
      CONTENT
    </div>
  </div>
</div>
.header{
    position: relative;
    background-color: #f00;
    width: 100%;
    height: 100px;
    text-align: center;
    line-height: 100px;
    color: #fff;
}

.body{
  position: relative;
  width: 100%;
  height: auto;
}

.menu{
    float: left;
    position: relative;
    width: 30%;
    height: 200px;
    background-color: #0f0;
}

.content{
  float: right;
  position: relative;
  width: 70%;
  height: 200px;
  background-color: #00f;
  color: #fff;
}