css中的左右垂直居中的问题，可兼容各种版本浏览器的写法

目前主流的css布局包含：居中布局、多列布局、全屏布局。

主要样式参考：

<style type="text/css">
        html,body,p,h1,h2,ul,li{
            margin: 0;
            padding: 0;
            list-style: none;
        }
        .main ul{
            display:flex;
            flex-direction: row;
            justify-content: space-between;
            padding:20px;
        }
        .main div{
              width: 200px;
              height: 200px;
              text-align: center;
              margin-bottom: 10px;
              background-color: #faa755;
        }
        .main div p{
            width: 100px;
            height: 50px;
            background-color: #fedcbd;
        }
        /*水平居中*/
        .center-line-inline{
            display:inline-block;
            text-align: center;
        }
        .center-line-inblock{
            margin:0 auto;
            text-align: center;
        }
        .center-line-flex{
            display:flex;
            flex-direction: row;
            justify-content: center;
        }

        /*垂直居中*/
        .center-row{
            display: table-cell;
            vertical-align:middle;
        }
        .center-row-position{
            position:relative;
            margin-top:10px;
        }
        .center-row-position p{
            position: absolute;
            top:50%;
            left:0;
            margin-top: -25px;
        }
        .center-row-flex{
            display:flex;
            align-items: center;
        }
        /*水平垂直居中*/
        .center-all{
            display: table-cell;
            text-align: center;
            vertical-align:middle;
        }
        .center-all p{
            display: inline-block;
        }
        .center-all-position{
            position: relative;
            margin-top:10px;
        }
        .center-all-position p{
            position:absolute;
            left:50%;
            top:50%;
            margin-top:-25px;
            margin-left:-50px;
        }
        .center-all-flex{
            display:flex;
            align-items: center;
            justify-content: center;
        }

        /*圣杯布局*/
        .main .grail-box{
            width: 100%;
            height: 600px;
            position:relative;
        }
        .main .grail-box .center{
             background:#feeeed;
             width: 100%;
             height: 600px;
        }
         .main .grail-box .left{
            background:#f391a9;
            width: 200px;
            height: 600px;
            position:absolute;
            left:0;
            top:0;
         }
        .main .grail-box .right{
           background: #4e72b8;
           width: 200px;
           height: 600px;
           position:absolute;
           right:0;
           top:0;
        }

        .main .grail-box-fl{
            width: 100%;
            height: 600px;
            overflow: hidden;
        }
        .main .grail-box-fl .center{
            background:#feeeed;
            width: calc(100% - 400px);
            height: 600px;
            float:left;
        }
        .main .grail-box-fl .left{
            background:#f391a9;
            width: 200px;
            height: 600px;
            float:left;
         }
         .main .grail-box-fl .right{
           background: #4e72b8;
           width: 200px;
           height: 600px;
           float: left;
        }
    </style>

一、居中布局

<ul>
    <li>
      <h2>水平居中</h2>
      <div>
          <p class="center-line-inline">水平居中1</p>  <!-- 块级元素：text-align:center -->
      </div>
      <div>
          <p class="center-line-inblock">水平居中2</p>  <!-- 块级元素：margin:0 auto -->
      </div>
      <div class="center-line-flex">
          <p>水平居中3</p> <!-- 弹性盒模型 justify-content: center;-->
      </div>
    </li>
    <li>
      <h2>垂直居中</h2>
      <div class="center-row">
          <p class="center-row-inline">垂直居中1</p> <!-- vertical-align:该属性定义行内元素的基线相对于该元素所在行的基线的垂直对齐(大白话就是相对于同一行元素来说)，所以使用此属性布局垂直居中，需要设置父级元素属性为表格属性 -->
      </div>
      <div class="center-row-position">
          <p>垂直居中2</p>  <!-- 通过定位计算，需要知道子元素的高度 -->
      </div>
      <div class="center-row-flex">
          <p>垂直居中3</p>  <!-- 弹性盒模型 align-items: center; -->
      </div>
    </li>
    <li>
      <h2>水平垂直居中</h2>
      <div class="center-all">
          <p>居中1</p>    <!-- vertical-align结合align-center-->
      </div>
      <div class="center-all-position">
          <p>居中2</p>    <!-- 通过定位计算，需要知道子元素的宽高-->
      </div>
      <div class="center-all-flex">
          <p>居中3</p>    <!-- 通过弹性盒模型-->
      </div>
    </li>
  </ul>

二、多列布局（两列/三列布局、圣杯布局）

<h1>多列布局</h1>
  <h2>圣杯布局</h2> <!--  (左右固定中间自适应)(中间栏要在浏览器中优先渲染) -->
  <div class="grail-box"> <!--  通过绝对定位 -->
      <p class="center">中qqq</p>
      <p class="left">左</p>
      <p class="right">右</p>
  </div>
  <div class="grail-box-fl"> <!--  通过浮动 -->
      <p class="left">左</p>
      <p class="center">中</p>
      <p class="right">右</p>
  </div>

收藏：圣杯布局和双飞翼布局的理解与思考

三、全屏布局（等分布局、等高布局、全屏布局）