<!-- Any copyright is dedicated to the Public Domain. http://creativecommons.org/publicdomain/zero/1.0/ --> <!-- Helper-file for reftest flexbox-resizeviewport-1.xhtml I'm intentionally using quirks-mode (no doctype), so that a 100% height will work. --> <html> <head> <style> div.flexbox { display: flex; height: 100%; border: 2px dashed black; } div.a { flex: 1; background: pink; } div.b { flex: 1; background: teal; } </style> </head> <body> <div class="flexbox"> <div class="a"></div><div class="b"></div> </div> </body> </html>