<!DOCTYPE HTML> <title> absolutely positioned element should be vertically centered even if the height is bigger than that of the containing block (reference) - bug 812899</title> <style> body > div { font-size: 16px; position: relative; border: red solid; margin-top: 5em; width: 5em; height: 5em; } body > div > div { position: absolute; border: medium solid blue; margin: auto auto; height: 150%; width: 150%; left: 0px; right: 0px; top: 0px; bottom: 0px; } </style> <body> <div> <div></div> </div> </body> </html>