CSS child element set float, parent element height collapsed

Take the div element as an example. The height of the div element is automatically stretched through the content. That is, how much content, how high it is. But when the inner element sets the float property, the parent element is highly collapsed

<class= "container">       <p> Hello world! Hello world! </ P >       <  class= "Clearfix"></div></  div>

How to clear floating

Add an empty div at the bottom of the parent element, and then add the property Clear:both

{  overflow: hidden;   *zoom: 1;}

Parent element set pseudo-class after

{  content: "";   display: table;   Clear: both;}

CSS child element set float, parent element height collapsed