Whether to display Spell Activation Overlays (a.k.a. Spell Alert system introduced in 4.0.1).
Changing this setting
In-game, type the following
/console displaySpellActivationOverlays setting
Alternatively, you can exit wow, open the Config-cache.wtf file, and add the following line:
SET displaySpellActivationOverlays setting
Patch 4.0.1 (2010-10-12): Added