ie 居中方案

    <style>
        #root{ /*父元素*/
            width: 500px;
            height: 500px;
            display: table;
        }

        #root .no1{ /*子元素*/
            display: table-cell;
            vertical-align: middle; /*上下居中*/
            text-align: center; /*左右居中*/
        }
    </style>

    <div id="root">
        <div class="no1">1</div>
    </div>

    <style>
        #root{
            width: 500px;
            line-height: 500px;
            background-color: red;
        }

        #root .no1{
            width: 100%;
            display: inline-block;
            vertical-align: middle;
            text-align: center;
        }
    </style>

    <div id="root">
        <div class="no1">1</div>
    </div>

    <style>
        #root{
            width: 500px;
            height: 500px;
            position: relative;
            background-color: red;
        }

        #root .no1{
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%);
        }
    </style>

    <div id="root">
        <div class="no1">1</div>
    </div>