sth is not right with that balance checker on main page. If i enter random addresses it gives some output different from 0.
the balance checker is pretty basic, it just checks the total outputs from an address.. it assumes the address was generated on the site.. so any address generated on the site should have a balance of 0 , with the total spent equal to amount of investment.
yes, any bitcoin address with outputs will give you a balance. thats why you should only be entering in the btcaddr from the downloaded file or email received.