Uncanny Accuracy( Epic Level Handbook, p. 68)
You can ignore anything less than total cover or total concealment when using ranged weapons.
When throwing or shooting a ranged weapon, you can ignore any cover bonus to the target's AC (up to a maximum of nine-tenths cover) or any miss chance conferred by the target's concealment (up to a maximum of nine-tenths concealment). If the target has total concealment or total cover, the AC bonus or miss chance applies normally.
3.5 Update: Your ranged attacks ignore the miss chance granted to targets by total concealment. You must aim your attacks at the correct square to gain the advantage of this feat.
3.5 Update: A character with at least 11 levels of ranger can qualify for this feat even if he does not have the prerequisites for it, but can only use it when wearing light armor or no armor.
3.5 Update: Without this feat, you suffer a 50% miss chance when making a ranged attack against a target with total concealment