Created attachment 573857 [details]
User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_2) AppleWebKit/534.51.22 (KHTML, like Gecko) Version/5.1.1 Safari/534.51.22
Steps to reproduce:
Run the attached file.
The red box should be centered. If you open up the code and comment out line 22, the red box becomes centered.
The CSS "display:-moz-box" causes the box to not respect "margin:0 auto".
Almost certainly wontfix; that's just not what margins do with -moz-box.
Note that -moz-box isn't related to the current CSS flexbox spec.