What you are seeing on your bank account is an authorization or a "pending charge". This is a common bank practice for handling credit card transactions to ensure sufficient funds and account authenticity. If your order was declined or canceled, this authorization will clear on its own.
An authorization hold (or preauthorization) is the practice within the banking industry of authorizing electronic transactions done with a debit card or credit card and holding this balance as unavailable either until the merchant clears the transaction (also called settlement) or the hold "falls off." Debit card authorization holds can fall off the account (rendering the balance available again) anywhere from 1–8 days after the transaction date depending on the bank's policy. Credit card holds may last as long as 30 days, depending on the issuing bank.