http://druid.wikispaces.com/Hit_Rating wrote:
Some information about +Hit and Feral Combat Skill Rating:
* Any player or mob has a 5% base chance to miss.
* Any mob has a 5% base chance each to dodge, parry and block.
* The amount of +hit needed against higher leveled mobs increases exponentially.
* +hit (and some buffs or talents) are the only way to reduce miss chances. Agility does NOT help to hit.
* Miss chance can be dropped to 0%, so you can effectively eliminate the chance of ever missing an attack in melee combat. This works differently for spells where there will always be at least a 1% chance to have your spell "miss" (aka. resisted) no matter how much +spellhit gear you have.
For Raids:
* Hence, a player has 9% miss chance vs a Boss
* 142 Hit Rating covers the 9%.
thats TBC info