(b)  Yes, that's right.  Generally speaking, advertising goods or services online is the same as displaying them in a shop or advertising them in printed media – that is to say, the online advertisements constitute an ‘invitation to treat’ rather than an ‘offer’ in the contractual sense. It is when the customer indicates that they are willing to buy specified goods or services at an agreed price that the contractual offer takes place. 

This is normally done by the buyer selecting the desired goods (as described by the seller) and entering the details of how they will make payment. They then send this ‘offer to purchase’ electronically to the seller. Acceptance of the offer by the seller also takes place electronically, through a message sent to the buyer acknowledging the order and accepting the offer. At this stage, a contract comes into existence.

Typically, the acceptance of the offer and processing of the payment take place very close together, but they are still separate aspects of the transaction.  The processing of the buyer’s payment, and delivery of goods or services, constitutes performance of the contractual duties, a matter dealt with in separate modules.