1,Flexbox(更优雅的布局)
①居中：{display:flex; justify-content:center; align-items:center;}
②设定flex-grow属性的话，会自动填满空白;
③原理：display:flex就是flex:0 0 auto就是flex-grow:0;flex-shrink:0;flex-basic:auto
2，text-align: justify;text-align-last:justify;（多列均匀布局）
也可以用伪类：.justify:after {content: "";display: inline-block;width: 100%;}