css实现高度或者宽度不固定的div元素垂直左右居中

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
    .demo {
        line-height: 44px;
        margin-bottom: 20px;
        text-align: center;
        background-color: #0078e7;
        color: #fff;
    }
    .flex-equal, .flex-center, .justify {
        display: -webkit-box;
        display: -ms-flexbox;
        display: -webkit-flex;
        display: flex;
    }

    .flex-center {
        -webkit-box-pack: center;
        -ms-flex-pack: center;
        -webkit-justify-content: center;
        justify-content: center;
        -webkit-box-align: center;
        -ms-flex-align: center;
        -webkit-align-items: center;
        align-items: center;
    }
    .demo-center .children {
        background: #0078e7;
        color: #fff;
        width: 150px;
        line-height: 5;
        text-align: center;
    }
    .demo-center {
        border: 1px solid #ccc;
        margin: 20px;
        height: 200px;
    }

    .translate-center {
        position: relative;
    }
    .demo-center .children {
        background: #0078e7;
        color: #fff;
        width: 150px;
        line-height: 5;
        text-align: center;
    }
    .translate-center .children {
        position: absolute;
        top: 50%;
        left: 50%;
        -webkit-transform: translate(-50%, -50%);
        transform: translate(-50%, -50%);
    }

    .table-equal {
        display: table;
        table-layout: fixed;
        width: 100%;
    }
    .table-equal li {
        display: table-cell;
    }
    .container {
        width: 100%;
        height: 80px;
        background: #C2300B;
        padding-top:10px;
        text-align:center;
    }
    .center{
        display:inline-block;
        border:2px solid #fff;
    }
    .center{
        _display:inline;
    } /*针对ie6 hack*/
    .center a{
        float:left;
        border:1px solid #fff;
        padding:5px 10px;
        margin:10px;
        color:#fff;
        text-decoration:none;
    }
    #vc {
        display:table;
        background-color:#000;
        width:100%;
        height:200px;
        overflow:hidden;
        margin-left:50px;
        _position:relative;
    }
    #vci {
        vertical-align:middle;
        display:table-cell;
        text-align:center;
        _position:absolute;
        _top:50%;
        _left:50%;
    }
    #content {
        color:#fff;
        border:1px solid #fff;
        display:inline-block;
        _position:relative;
        _top:-50%;
        _left:-50%;
     }
    </style>
</head>
<body>
    <h2>flex居中</h2>
    <div class="flex-center demo-center">
        <div class="children">子元素水平垂直居中</div>
    </div>
    <h2>translate居中</h2>
    <div class="translate-center demo-center">
        <div class="children">子元素水平垂直居中子元素水平垂直居中</div>
    </div>
    <h2>div宽度不固定的div如何设置水平居中</h2>
    <div class="container">
        <div class="center">
           <a href="#">1</a><a href="#">2</a><a href="#">3</a>
        </div>
    </div>
    <h2>table居中高度不固定的div垂直居中</h2>
    <div id="vc">
        <div id="vci">
            <div id="content">
                我们垂直居中了，我们水平居中了,真的是可以居中的吗，<br />
                你信不信我反正是新了<br />
                年轻化互联网团队！
            </div>
        </div>
    </div>
</body>
</html>