Both - Move the generated box below all floating boxes generated from previous source elements.
both -将所生成框移动到由之前的源文档所生成的所有浮动框之下。
2
The right outer edge of a left-floatingbox may not be to the right of the left outer edge of any right-floatingbox that is next to it.
在浮动元素之前是一行行内元素，所以浮动盒子就没有超过文本的最后一行的顶部。
3
The outer top of a floatingbox may not be higher than the outer top of any block or floated box generated by an element earlier in the source document.