Help with all your problems and a Review
First off, MHC is a very fun, addicting game where you can meet and chat, take care of horses, compete, breed and even more. Sure it costs real money to get extra horses, tack, and that but it is still possible to play the game without spending any real money at all. You might even meet friends who will give you free stuff or you can trade stuff for extra things. You also can earn clops, a free money thingy and you can buy extra supplies with clops.
Alright now for why it's not loading has two reasons, either you pressed yes to the security popup or you downloaded the wrong version of java. They made a mistake and provided the 6.24 version but you need the 6.23 version.
Finally if you do play MHC, I'm Kona164 on it :)