I learn from Euclid Managers Insurance Blogthat the U.S. Court of Appeals for the Ninth Circuit (it covers California) has confirmed that the answer to the question of whether a service provider may change the terms of its service contract by merely posting a revised contract on its website is NO. Let me repeat that: NO.
This result, I would have thought, is the only one consistent with established principles of contract law (which do not differ across the English-speaking world), but as always some clients can find lawyers to agree to defy logic on their behalf.
The Ninth Circuit inter alia noted that the customer:
... could only have learned of the new contract terms by going to the company’s website and examining the contract for changes. Without notice, a party wouldn’t know when to check a website and might have to do it as often as daily. And a person would have to compare every word of the original contract with the posted contract in a search for changes
Then the court addressed concepts of contract law: parties to a contract are not obligated to check the terms to learn whether they have been changed by the other side. A party can’t by itself change the terms of an agreement; it must first obtain the other party’s consent. A “revised contract” put forth by one party is nothing more than an offer that is not binding until accepted by the other party. And generally an offeree cannot actually consent to an offer unless he knows it exists....
The above quotations are extracted from T. R. Franklin's article on Euclid Managers Insurance Blog, which I encourage you to read and, indeed, to which a subscription would be a good idea.