My "faith" that there is no God is founded in the fact that there is absolutely zero scientific evidence to suppose his/her/its existance.
A good quote I once heard, of an atheist talking to a devout Christian:
"You and I are very similar, having near identical theological views".
"Really?" Says the Christian.
Yes, the atheist replies, "There are 2500 Gods or deities, from the most ancient gods of polytheistic societies - Hittite, Sumerian, Mesopotamian - to the most contemporary gods of the major monotheistic religions - Allah, God, Yahweh"
You don't belive in 2,499 of them, whereas I don't believe in 2,500.