Changing HUD mode

[Moonroc]

In a recent dungeon, I somehow managed to change my HUD from Player/Target mode to Health/Power. I'd like to get it back the way it was, but I can't find out how to do it. I did some searching and found something about a red button at the top of the screen, but I have no such animal... Is there a slash command that will make the change?? Am I missing something obvious?? Thanks in advance...