css水平居中和垂直居中

水平居中：
内联元素：text-align:center;相对于父级居中显示
块级元素：margin:0 auto;但是需要同时width，否则无法看到效果
多个块级元素居中：在此想要探讨一下display:inline-block;和display:flex;
方法1：在父级上设置text-align:center;在元素上设置:display:inline-block;同时为了使文字向左显示，设置了text-align:left;在浏览器中的显示为，子元素高度自适应，底部对齐。
方法2：在子元素上设置display:center;justify-content:center;子元素的高度一致，与元素中内容最多的高度相同。
二种方法在谷歌，火狐，360均兼容，但是第2种方法在IE10中不兼容，之前的IE版本可想也是不兼容的。当然在此也要处理由于浮动导致离层，父级背景颜色加不上去的问题。

<main class="inline-block-center">
  <div>
    I'm an element that is block-like with my siblings and we're centered in a row.
  </div>
  <div>
    I'm an element that is block-like with my siblings and we're centered in a row. I have more content in me than my siblings do.
  </div>
  <div>
    I'm an element that is block-like with my siblings and we're centered in a row.
  </div>
</main>

<main class="flex-center">
  <div>
    I'm an element that is block-like with my siblings and we're centered in a row.
  </div>
  <div>
    I'm an element that is block-like with my siblings and we're centered in a row. I have more content in me than my siblings do.
  </div>
  <div>
    I'm an element that is block-like with my siblings and we're centered in a row.
  </div>
</main>

body {
  background: #f06d06;
  font-size: 80%;
}
main {
  background: white;
  margin: 20px 0;
  padding: 10px;
}
main div {
  background: black;
  color: white;
  padding: 15px;
  max- 125px;
  margin: 5px;
}
.inline-block-center {
  text-align: center;
}
.inline-block-center div {
  display: inline-block;
  text-align: left;
}
.flex-center {
  display: flex;
  justify-content: center;
}

垂直居中：

方法1：设置padding-top和padding-bottom的值相等
方法2：设置height和line-height的值相等
方法3：固定高度可以有一种处理方式position:absolute;top:50%;height:100px;margin-top:-50px;如果高度不固定，也可以使用js动态获取高度来。
还有css3的一些属性，考虑到兼容性问题不在叙述。