Is there a side of the neck which the mane should be on? I am asking this because at my barn there are only 4 or 5 horses out of almost 40 that have there manes lying on the left side.
That's actually very true. I read that almost all horses are basically right handed (or hooved) The mane will fall on the dominant side. Training it to go the opposite way is like training a child to hold the pencil with the right hand when it wants to hold it with the left.It is like being right handed or left handed. There are more right handed people then left but neither is wrong. That being said some type or events of shows have what they consider to be norms. It comes down to history in some cases. It is the way it has always been done so we keep doing it. Past that there is no reason.