1. A context management method carried out in a network system in which a plurality of computers is connected to a network, the method comprising: creating or updating a shared field which is accessible by a plurality of users through a plurality of computers, respectively, wherein creating or updating the shared field is carried out by one of the computers connected to the network; storing a shared-field context in a first memory area on the network, wherein storing the shared-field context is carried out by the computer which carried out creating or updating the shared field, the shared-field context describes at least one of features of the shared field, the features are caused within the shared field by inputs from the users accessing the shared field or by interactions among the plurality of users, and; storing a user context as well as a reference in a second memory area on the network, wherein storing the user context as well as the reference is carried out by each of the computers accessing the shared field, the user context is a context which is unique to a user operating one of the accessing computers and is caused within the shared field by an input from the operating user or by the interaction associated with the operating user, and the reference is usable for referring to the first memory area, wherein each user of the plurality of users is led to obtain, though an arbitrary one of the computers, the user context of the each user stored in the second memory area or the shared-field context of the shared field, which the user accessed, by the use of the reference stored in the second memory area, wherein one of the computers connected to the network obtains the user context from the second memory area and accesses the shared field or a different shared field in connection with the obtained user context, which concerns the user operating the computer in question.