三栏布局将主页分成3部分左中右,左右定宽，中间自适应

1.浮动实现
兼容好，易实现
左右浮动，再写中间，需要去浮动

<style>
        .left {
            width: 100px;
            height: 100px;
            background: lightcoral;
            float: left;
        }
        .right {
            width: 100px;
            height: 100px;
            background: lightskyblue;
            float: right;
        }
        .center {
            margin: 0 100px;
            height: 100px;
            background: mediumpurple;
        }
    </style>
    <div class="left"></div>
    <div class="right"></div>
    <div class="center"></div>

2.定位实现
左右分别定位两侧，中间左右margin 和左右宽度一致
脱离文档流，顺序正常

 <style>
        *{
            margin:0;
            padding: 0;
        }
        .left {
            width: 100px;
            height: 100px;
            background: lightcoral;
            position: absolute;
            left: 0;
            right: 0;
        }
        .right {
            width: 100px;
            height: 100px;
            background: lightskyblue;
            position: absolute;
            right: 0;
            top: 0;
        }
        .center {
            height: 100px;
            background: mediumorchid;
            margin: 0 100px;
        }
   </style>
    <div class="left"></div>
    <div class="center"></div>
    <div class="right"></div>

3.flex实现

<style>
        *{
            margin:0;
            padding: 0;
         }
        .container {
            display: flex;
        }
        .left {
            width: 100px;
            height: 100px;
            background: lightskyblue;
        }
        .right {
            width: 100px;
            height: 100px;
            background: orangered;
        }
        .center {
            height: 100px;
            background: orchid;
            flex: 1;
        }
    </style>
   <div class="container">
        <div class="left"></div>
        <div class="center"></div>
        <div class="right"></div>
    </div>