"God" exists, it's not what's written in books or what most religions claim though.
It's us, and the rest of the universe - it's not matter though, it's what matter is made of.
And that's not atoms or quarks... it's what that is made of - the closest definition in science as of yet is "energy".
You want some signs of the "classic" God's non-existance?
Read my next lines carefully:
God, if You exist and is all-seeing... then don't let me submit this post.
Also make me pass out NOW if You think people should keep their faith in You.
Make sure You do that before I write my next line here... :
Hrm-hrm... hi folks, I'm still here!
Ooh.. I'm such a rebel hehe.