DIV 居中

.container {
    position: absolute; left: 50%; top: 50%;
    transform: translate3d(-50%, -50%, 0);
}

.container{
    margin:0 auto;
}

<div class="container">
    <div class="sub-container"></div>
</div>

.container{
    width:200px;
    height:100px;
    position: absolute;
    top:50%;
    left:50%;
}
.sub-container{
    width:100%;
    height:100%;
    margin-top:-50%;
    margin-left:-50%;
}