水平垂直居中的几种方式-案例

<iframe height="880" style="width: 100%;" scrolling="no" title="水平垂直居中的几种方式" src="https://codepen.io/xugaoyi/embed/poJLeYv?height=880&theme-id=light&default-tab=result" frameborder="no" allowtransparency="true" allowfullscreen="true"> See the Pen <a href='https://codepen.io/xugaoyi/pen/poJLeYv'>水平垂直居中的几种方式</a> by xugaoyi (<a href='https://codepen.io/xugaoyi'>@xugaoyi</a>) on <a href='https://codepen.io'>CodePen</a>. </iframe>