左右经典布局

左右两列：一列宽度固定，一列宽度自适应

 * {      box-sizing :border-box;    }    body {      background-color: #ddd;      text-align: center;    }    .main, .left {      background-color: #fff;    }    .main {      margin-left: 210px;      float: left;      width: calc(100% - 210px);    }    .left {      float: left;      width: 200px;      margin-left: -100%;    } ``````html <div class="main">    <p>this is main</p>    <p>this is main</p>    <p>this is main</p>    <p>this is main</p>    <p>this is main</p>  </div>  <div class="left">left</div>