What are the arrows that I see under some users names? Is there a spell checker built into this program?
There's no spell checker at the moment; we may add one in the coming months. You could always use Firefox, which has a spell checker built in.
How do you get and loose karma?
Karma is given to you by other people who read your posts. If they like what you wrote, they can award you some karma in appreciation. It's just a way of saying "thanks".
If you accumulate 1,000,000 karma points, we'll give a coupon good for dinner. (I'm kidding!)