[veonik]

"One small step for a man" is what he actually said, I think, or so I've heard. Apparently the "a" was lost due to radio interference.

[bluGill]

Wikipedia (see elsewhere for link) has good coverage of that. "A" was intended to be said, but when humans say lines like that it is common to miss a word here and there. There is no way to know for sure if he said it and the technology of the time didn't pick it up, or if he misstated his own quote.