<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <script> function boom() { document.documentElement.offsetHeight; document.body.appendChild(document.getElementById("x")); document.documentElement.offsetHeight; } </script> </head> <body style="-moz-column-count: 4;" onload="boom();"> <div style="float: left; height: 10px; width: 10px;"> <div id="x"> <div style="height: 80px;"></div> <div style="float: left; height: 10px;"></div> </div> </div> </body> </html>