e-commerce selling service

hi dudes!

I was just wondering, if your going to create a site to sell a service, thats not critical to much, just a fun thing to have, what kind of legal problems might there be?

if, say your selling avatars for people to use in a forum, but they're hosted on your site and someone has paid $10 for an or set of avatars that randomly rotate and the server goes down and they stop, whatr kind of clause do you need in your terms?

thanks,
computer