Again, you are no position to post that, as you cannot disprove its external effects on an indivdual, a population or events past or present. You are better off limiting your opinion to one representing yourself.
This has been studied. There is no reason to believe that prayer has effects distinguishable from random chance or a placebo effect. Funnily enough telling sick people that they were prayed for made them slightly worse (reason is a bit unclear, possibly because this made them more worried, increasing stress.)
Furthermore you don't need to prove that something isn't real, you have to prove that something is real. If I claim that wearing a special red magic hat of my design will make you more succesful in life, I better to be able to prove that.