这样的效果是，一个被清理的盒没法与前置浮动保持在同一个级别位置上。

So in effect, such a cleared box cannot be at the same horizontal level as a PageRankeceding float.

youdao

这是将被清除盒的顶部边距扩展，将其向下推直到清理浮动的底部。

What this does is extend the margin on the top of the cleared box, pushing it down until it "clears" the bottom of the float.

youdao

展示一个盒如何清理下方的一个浮动。

Shows how a box may clear below a float.

youdao