My advice? He'll probably overcome that as he gets older but for now..with his age, I'd probably keep him off the stairs altogether. Actually, since I'm being honest...I'd block the stairs until he got older and then I'd put something for traction like carpeting on the stairs. I know that can be costly, but I've heard of these littles falling off of and down stairways. A broken leg or worse will cost more than carpet.
Hang in there, though. The stair phobia (seeing how far down it is when one is so little) is normal but usually it is grown out of.
