Australian Competition and Consumer Commission:

Before participating in an online auction it’s important to read the terms and conditions and understand all procedures and costs.

Some auction sites give you an option to buy now without having to bid. If you choose to buy immediately you will have all your usual shopping rights,   unless the seller is a private individual and it is a one-off sale.

http://www.accc.gov.au/consumers/online-shopping/online-auctions