<div id="wrap">
  <div id="header"></div>
  <div id="nav"></div>
  <div id="main">
    <div id="aside"></div>
    <div id="section"></div>
    <div id="article"></div>
  </div>
  <div id="footer"></div>
</div>

* {
  margin: 0;
}
body {
  background-color: #e8f4f5;
}
#wrap {
  width: 1200px;
  margin: 0 auto;
}
#header {
  width: 100%;
  height: 100px;
  background-color: #c8e6c9;
}
#nav {
  width: 100%;
  height: 100px;
  background-color: #a5d6a7;
}
#main {
  width: 100%;
  overflow: hidden;
}
#aside {
  width: 30%;
  height: 780px;
  background-color: #81c784;
  float: left;
}
#section {
  width: 40%;
  height: 780px;
  background-color: #66bb6a;
  float: left;
}
#article {
  width: 30%;
  height: 780px;
  background-color: #4caf50;
  float: left;
}
#footer {
  width: 100%;
  height: 100px;
  background-color: #43a047;
}
@media (max-width: 1300px) {
  #wrap {
    width: 96%;
  }
}
@media (max-width: 768px) {
  #wrap {
    width: 100%;
  }
  #aside {
    width: 30%;
    height: 630px;
  }
  #section {
    width: 70%;
    height: 630px;
  }
  #article {
    width: 100%;
    height: 150px;
  }
}
@media (max-width: 480px) {
  #aside {
    width: 100%;
    height: 200px;
  }
  #section {
    width: 100%;
    height: 430px;
  }
}