I polyurethaned my table and when it dried, it had spots. That is the best way to explain it. It looks like the eraser-sized spots are bare wood, almost like something made the polyurethane push away from the wood as it dried, leaving 100 spots on the table. I lightly sanded it and it just looks like the spots are lower than the smooth polyurethane. Almost like the wood just repelled the polyurethane. So I lightly sanded and then re-applied another coat and as it dried, what do you know... the spots came right back like the polyurethane did not want to stick to the wood in those eraser-sized spots.
So for those experienced wood workers out there, please help me with this baffling issue to try to get a smooth application.