From Diablo Wiki
Attack rating is a number that indicates a player's chance to hit (either a monster or another player). It is increased by adding points into the character attribute Dexterity. The higher one's attack rating, the higher one's chance to hit.
Chance to hit has a maximum of 95% and a minimum of 5%.
The Sorceress's spells and other casting spells are not affected by attack rating.
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