CSS左右固定

<style>
    .left{
        width: 200px;
        float: left;
        background-color: pink;
    }
    .right{
        width: 200px;
        float: right;
        background-color: pink;
    }
    .center{
        margin: 0 200px; background-color: lightskyblue;
    }
</style>
<div class="left">左边固定宽度</div>
<div class="right">右边固定宽度</div>
<div class="center">中间自适应</div>