Currently staying with DH's family, got a 9 month old baby and getting fed up with the 'advice' now! Usually food related. Examples:
In response to current advice which says no more than 1g of salt a day for babies: "We gave all my children and grandchildren lots of salty food when they were babies and they came out fine!"
"I'll make him some warm sugary milk, that's what he wants when he wake up crying in the night!" I'll admit this one was quite sweet. DS woke up around midnight probably due to teething pain, was screaming for quite a while, DH's 75 yr old nan comes upstairs in her frilly nightgown with a bottle of warm cows milk (he's breastfed!), I tested a bit and it was the sweetest thing I've ever tasted, god knows how much sugar she added!
Also today DH got very angry with his nan for giving baby a piece of bread slathered in honey after he strictly told her the day before that babies mustn't have honey.
None of this particularly enrages me, they do mean well, it's just a bit annoying after a while when they insist on going against current advice...