两栏布局和三栏布局

1. 双栏布局

• 使用float左浮左边栏
• 右边模块使用margin-left撑出内容块做内容展示
• 为父级元素添加BFC，防止下方元素飞到上方内容

<style>
    .box{
        overflow: hidden; 添加BFC
    }
    .left {
        float: left;
        width: 200px;
        background-color: gray;
        height: 400px;
    }
    .right {
        margin-left: 210px;
        background-color: lightgray;
        height: 200px;
    }
</style>
<div class="box">
    <div class="left">左边</div>
    <div class="right">右边</div>
</div>
采用弹性布局也可
<style>
    .box{
        display: flex;
    }
    .left {
        width: 100px;
    }
    .right {
        flex: 1;
    }
</style>
<div class="box">
    <div class="left">左边</div>
    <div class="right">右边</div>
</div>

---

2. 三栏布局

• 两边使用float，中间使用margin
• 两边使用absolute，中间使用margin
• 两边使用float和负margin
• display：table实现
• flex实现
• grid网格布局

<style>
    .wrap {
        background: #eee;
        overflow: hidden; <!-- 生成BFC，计算高度时考虑浮动的元素 -->
        padding: 20px;
        height: 200px;
    }
    .left {
        width: 200px;
        height: 200px;
        float: left;
        background: coral;
    }
    .right {
        width: 120px;
        height: 200px;
        float: right;
        background: lightblue;
    }
    .middle {
        margin-left: 220px;
        height: 200px;
        background: lightpink;
        margin-right: 140px;
    }
</style>
<div class="wrap">
    <div class="left">左侧</div>
    <div class="right">右侧</div>
    <div class="middle">中间</div>
</div>

<style>
  .container {
    position: relative;
  }
  
  .left,
  .right,
  .main {
    height: 200px;
    line-height: 200px;
    text-align: center;
  }

  .left {
    position: absolute;
    top: 0;
    left: 0;
    width: 100px;
    background: green;
  }

  .right {
    position: absolute;
    top: 0;
    right: 0;
    width: 100px;
    background: green;
  }

  .main {
    margin: 0 110px;
    background: black;
    color: white;
  }
</style>

<div class="container">
  <div class="left">左边固定宽度</div>
  <div class="right">右边固定宽度</div>
  <div class="main">中间自适应</div>
</div>

<style>
  .left,
  .right,
  .main {
    height: 200px;
    line-height: 200px;
    text-align: center;
  }

  .main-wrapper {
    float: left;
    width: 100%;
  }

  .main {
    margin: 0 110px;
    background: black;
    color: white;
  }

  .left,
  .right {
    float: left;
    width: 100px;
    margin-left: -100%;
    background: green;
  }

  .right {
    margin-left: -100px; /* 同自身宽度 */
  }
</style>

<div class="main-wrapper">
  <div class="main">中间自适应</div>
</div>
<div class="left">左边固定宽度</div>
<div class="right">右边固定宽度</div>