User blog comment:Rupert Giles/Global Navigation Update/@comment-452-20141202163302/@comment-24025240-20141202193416

The three designs will be randomized per user. If you are placed in an experimental group you should remain in that group for every subsequent pageview. If you clear your cookies or use a different browse you may end up in a different group.

As for the control group we are carving out a portion of the new nav traffic to act as a control. We've run previous experiments to arrive at this particular design so it is acting as the control.

And finally we have a bug filed with this descrption: "when you click "show changes" while previewing your edit, the bar covers the close button and you're unable to close the show changes screen." Is that the issue you are referring to?