http://geekplux.com/2014/03/14/collapsing_margins.html
垂直
https://read01.com/gm0eN.html
css - Margin collapse on inline-block elements? - Stack Overflow
http://stackoverflow.com/questions/25455932/margin-collapse-on-inline-block-elements
collapsed margin
http://geekplux.com/2014/03/14/collapsing_margins.html
inline-block不會有影響block只影響上下,左右不會
先記錄先