Establishing an Offer
What is an Offer?
The first requirement of contract formation is that one party made an offer. An offer is a promise to enter into a contract, which is objectively seriously intended. The following factors are relevant to whether there has been an offer:
Tone and Humour
If the tone or setting of the conversation is informal or appears to be in jest, there is likely no offer: Blue v Ashley  EWHC 1928.
A vague or equivocal statement is less likely to be an offer than a clear and unequivocal one: Blue v Ashley  EWHC 1928.
The party’s subjective state of mind is not relevant: Storer v Manchester City Council  3 All ER 824.
Invitations to Treat
Be careful to distinguish an offer from an invitation to treat. An invitation to treat is a statement which invites other people to make offers or negotiate. A person making an invitation to treat does not objectively appear to intend to be bound by the statement. For this reason, no contract arises if another person purports to accept an invitation to treat. Common situations which involve an invitation to treat and not an offer include:
If a person asks for information about a product and the defendant provides the information, the defendant’s response is normally an invitation to treat: Harvey v Facey  AC 552.
Goods in Shop Displays
Putting goods on display on a shelf or shop window is normally an invitation to treat: Pharmaceutical Society of Great Britain v Boots  1 QB 401. The customer makes the offer when they bring the goods to the counter.
Adverts are normally an invitation to treat: Partridge v Crittenden (1968) 2 All ER 421. However, they might not be if the wording demonstrates intention to be bound (such as by offering a reward): Carlill v Carbolic Smoke Ball  1 QB 256.
Catalogues, even when they include the price of the goods, are typically taken to be invitations to treat: Grainger & Son v Gough  AC 325.
An auctioneer asking for a bid is an invitation to treat: Payne v Cave (1789) 3 TR 148. However, in an auction ‘without reserve’, by inviting bids the auctioneer is also making a collateral offer to accept the highest bid price: Barry v Davies (2001) 1 WLR 1962.
While there is no case on whether goods displayed on a website are an offer or invitation to treat, it is likely that they are an invitation to treat. This is because the situation is analogous to shop displays.
Withdrawing an Offer
An offer can be revoked by the offeror any time before it is accepted: Payne v Cave (1789) 3 TR 148. This is so even if the offeror previously stated the offer would remain open for a particular period of time: Routledge v Grant (1828) 130 ER 920.
It is possible for a promise to keep the offer open to amount to a separate, collateral contract. However, consideration must be provided for that promise before it can be binding. Even if there is a collateral contract, the offeror can still withdraw the offer. He merely opens himself up to an action for breach of the collateral contract by doing so.
To withdraw an offer, the offeror must communicate the withdrawal to the offeree. He can do this in person or through a third-party. The offer is also treated as withdrawn if the offeree learns that the offeror has done some act inconsistent with the offer still being open (such as selling the subject matter of the offer to another person): Dickinson v Dodds (1876) 2 Ch D 463.
The postal rule (applicable to acceptances) is not applicable to offers: Byrne & Co v Leon Van Tien Hoven & Co  5 CPD 344.
Termination of Offers
An offer is terminated in the following circumstances:
Where the offer is rejected or a counter-offer is made: Hyde v Wrench (1840) 49 ER 132. Requests for information are not counter-offers: Stevenson, Jacques v McLean (1880) 5 QBD 346.
Lapse (Specific Period)
If a time for the offer lapsing is stated, when that time passes.
Lapse (Reasonable Period)
If no time is stated, when a ‘reasonable’ amount of time passes: Ramsgate Victoria Hotel v Montefoire (1866) LR 1 Ex 109. One case indicates that this only applies if the delay indicates that the offeree refuses the offer: Manchester Diocesan Council for Education v Commercial & General Investments Ltd  1 WLR 241.
If the offer is conditional, when that condition is fulfilled: Financings Ltd v Stimson  3 All ER 386.
Death of the Offeror
If the offeror dies, but possibly only in the case of contracts which need the offeror to personally perform: contrast Reynolds v Atherton (1922) 127 LT 189 and Bradbury v Morgan  158 ER 877.
Death of the Offeree?
Possibly if the offeree dies before accepting, as stated obiter in Reynolds v Atherton (1922) 127 LT 189.