“That you cannot prove God’s non- existence is accepted and trivial, if only in the sense that we can never absolutely prove the non-existence of anything. What matters is not whether God is disprovable (he isn’t) but whether his existence is probable. That is another matter. Some undisprovable things are sensibly judged far less probable than other undisprovable things. There is no reason to regard God as immune from consideration along the spectrum of probabilities. And there is certainly no reason to suppose that, just because God can be neither proved nor disproved, his probability of existence is 50 per cent.”Richard Dawkins, page 54, “The God Delusion”
You will find that the majority of atheist are actually agnostic as well. There is no conflict here as once deals with belief (atheist) and the other deals with knowledge (agnostic). I do not know if a god exists or not, but I do not believe one does.