<div class="main">
  <div class="aside">
        侧边栏
  </div>
  <div class="content">
        内容
  </div>
  <div class="footer">
     页脚
  </div>
</div>
.main {
  max-width: 500px;
  height: 300px;
  background: gray;
}
.aside {
  width: 100px;
  height: 300px;
  background: yellow;
  float: left;
}
.content {
  background: red;
}
.footer {
  clear: left;
  background: blue;
}

External CSS

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External JavaScript

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