Mission Control; how do I correct the order of Desktops? I have 1, 2, 4, 5, 3, 6, 7? I've been playing with Lion and Mission Control.  I'm not sure how I did it, but I seem to have reordered my desktops.

When I open Mission Control, the labels of the desktops at the top of the screen are (from left to right):

Dashboard, Desktop 1, Desktop 2, Desktop 4, Desktop 5, Desktop 3 (in the wrong place!), Desktop 6, Desktop 7, Desktop 8, Desktop 9

How did I relocate 3?  And how do I put it back in the right place?
By default, Spaces are reorganized by last used. You can change this in System Preferences -> Mission Control.