This reduces the likelihood that the agreement will be enforceable. Record the transaction. In addition to any other information you collect from each user at the time the user clicks to indicate acceptance, store the date and time of acceptance and the Internet Protocol address of the user, together with all the other data connected to the transaction. You can use that data to more easily prove the link between the click and the transaction. Retain samples of each online contract, keep track of when they were in use and provide copies to users who subsequently request them.
Most online agreements evolve with the business model.
So if a user asks for a copy of an agreement that she signed two years ago, make sure you can provide her with one.