问题
The question is simple and short: why does overflow: hidden; clear floating? I looked in to the w3 standard documentation and it did not imply anything.
回答1:
Because you establish a new Block Formatting Context when using overflow with anything ofther then visible (link to the w3.org specs).
来源：https://stackoverflow.com/questions/4910075/why-overflow-hidden-clears-a-float