Patch 7.0.3 (2016-07-19): Now learned at level 78 (was 80) and redesigned.
Previous effect: When you stand still for 3 sec, you gain Sniper Training for 6 sec, which increases your damage, shot range, and critical strike damage by 5%.
Patch 6.0.2 (2014-10-14): Re-added as the new Marksmanship Mastery. Effect simplified.
Previous effect: Increases the critical strike chance of your Kill Shot ability by 5/10/15%, and after remaining stationary for 6 sec, your Steady Shot and Cobra Shot deal 2/4/6% more damage for 15 sec.
Hotfix (2009-04-21):Sniper Training should no longer remove players from [Stealth].
Patch 3.1.0 (2009-04-14): Sniper Training has been changed to increase the critical strike chance of your [Kill Shot] ability by 5/10/15%, and while standing still for 6 sec., you gain Sniper Training increasing the damage done by your [Steady Shot], [Aimed Shot], [Black Arrow] and [Explosive Shot] by 2/4/6% Lasts 15 sec. (Previously increased damage and critical strike chance based on your range to the target.)