Bootstrap's Clearfix

Too many 1.div content will cause the div to be mangled later

<! DOCTYPE html>
　　
The source code in bootstrap is implemented by adding pseudo-classes and Clear:both, as follows:
. clearfix:before,.clearfix:after,.dl-horizontal dd:before,.dl-horizontal Dd:after,.container:before,.container: After,.container-fluid:before,.container-fluid:after,.row:before,.row:after,.form-horizontal. Form-group:before ,. form-horizontal. form-group:after,.btn-toolbar:before,.btn-toolbar:after,.btn-group-vertical >. Btn-group: Before,.btn-group-vertical >. btn-group:after,.nav:before,.nav:after,.navbar:before,.navbar:after,. Navbar-header:before,.navbar-header:after,.navbar-collapse:before,.navbar-collapse:after,.pager:before,.pager:  after,.panel-body:before,.panel-body:after,.modal-footer:before,.modal-footer:after {display:table; Content: "";}. Clearfix:after,.dl-horizontal Dd:after,.container:after,.container-fluid:after,.row:after,.form-horizontal. Form-group:after,.btn-toolbar:after,.btn-group-vertical >. btn-group:after,.nav:after,.navbar:after,. Navbar-header:after,.navbar-collapse:after,.pager:after,.panel-body:after,.modal-footer:after {Clear:both;}
　　
Bootstrap's Clearfix