Greg Koukl: Atheists’ Non-belief
People who claim that “God does not exist” bare a burden of proof. You can’t claim a universal negative (That something doesn’t exist anywhere in the universe. Why? Because we haven’t been everywhere in the universe.).
Even Richard Dawkins agrees that you can’t prove that there is no God.
Remember that anyone who believes something, theist or atheist alike, even if it’s a negative claim (a claim that something isn’t/can’t etc.) bares a burden of evidence.