Tried this last night- im new to the site, bare with me if already posted =P
basically this allows you to jump off cliffs and stuff and "pause" your character from moving
1) Put WoW in windows mode
2) jump from a ledge
3) when in midair, click and hold the bar at the top, as if you were trying to move the wow windows mode screen.
4) while you are holding it down, your character will not move while in the air. this can be proved because you when you resume the game, you will be in same exact spot you click-held it at.
my first post =p