css3 - 为什么css里面要带-moz-|-webkit-后又来一个不带它们的

Question

如

.three-column {
  padding: 1em;
  -moz-column-count: 3;
  -moz-column-gap: 1em;
  -webkit-column-count: 3;
  -webkit-column-gap: 1em;
  column-count: 3;
  column-gap: 1em;
}

这是出于什么目的呢？
说是浏览器兼容，但是既然浏览器支持这个属性了，直接column-count: 3;不就行了么？不支持的，这么加了也不支持的呀。

谢谢。

Answer 1

http://www.zhihu.com/question/19757263

Answer 2

The one without private prefix is ​​the standard way of writing HTML5. The reason why the one with prefix comes first and the standard way of writing it after is for forward compatibility.

Answer 3

Because these attributes are only experimental in nature, some browsers are afraid to expose them directly, so they add a prefix.

Answer 4

Do you understand the concept of object-oriented inheritance? I feel that the one without the prefix is ​​the parent class, and the one with the prefix is ​​the subclass, personal opinion. .