I don't understand why websites want to be hidden, being open about who you are increases credibility and builds up trust with your customers. I would think twice about using a site that didn't offer at the very least a postal address (not a PO Box) as a bare minimum.
It may be on there - maybe I can't see it for looking at it - its www.armcandyhire.com They looked like a new business that maybe I could see if they needed any accounting type work done for them. (and they could pay me in handbags!!)
I would read that link about web law and use it as a guide to finding online companies that use good business practice. Good luck.
If they are not registered with companies house different rules apply, but alwasy steer clear of PO box addresses and you can check addresses on the post office website by using their post code finder or address finder if you only have a postcode.