1. Log in using the Desktop Viewer
  2. Acquire Axis Test from http://maps.secondlife.com/secondlife/Testylvania%20Sandbox/125/140/21
  3. Wear it (On avatar center, should be default)
  4. Observe that the Blue Axis is pointing Z+
  5. Log in using the mobile viewer
  6. Observe that the Blue Axis is now pointing Y+
(Please excuse the picture quality on the mobile screenshot, you should still be able to make out that Green is pointing Z+ and Blue is pointing Y+).
This only seems to occur on the Avatar Center bone.