为何2 设置margin-top之后1 页跟着往下20px?;不是应该2相对于1往下20px么?
回复讨论(解决方案)
如果这样子,3会相对于2往下20px;
这是CSS 外边距合并特性
http://www.w3school.com.cn/css/css_margin_collapsing.asp
每个元素都有其默认的外边距,1是由默认的外边距,你设置2的外边距为20px,两个外边距会进行合并取较大值。
内边聚试下呢?不知道行不

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