<!DOCTYPE html> <!-- Any copyright is dedicated to the Public Domain. http://creativecommons.org/publicdomain/zero/1.0/ --> <html style="display: flex; justify-content: center"> <head> <title>CSS Reftest Reference</title> <link rel="author" title="Daniel Holbert" href="mailto:dholbert@mozilla.com"> <style> div { display: flex; justify-content: center; } </style> </head> <body> <div>centered</div> </body> </html>