The difference between an agnostic and an atheist is simple: one is a coward, the other is not.
You have to do all sorts of retarded mental gymnastics to say "There is no God" and somehow make that different from saying "I am certain there is no God."
A person doesn't "believe there is no God" while simultaneously believing he can't possibly know that.
Stop using the limitations of human knowledge (due to our spatio-temporal existence) as an excuse for theism.