When transferring funds between bitcoin addresses, you have to pay for the transaction fee. This fee is paid for the cost of the miners' operating equipment as the motivation system. After sending the transaction, the fee will be charged automatically from your wallet.
If you trade with all of the bitcoins in your LocalBitcoins wallet once and for all, the balance will be negative.
From the Billing page, you can download a excel file which contains all your transaction records of your BitcoinWorld accounts.