1. A task execution support system for supporting the execution of at least one task including a plurality of actions, comprising: a server machine which memorizes and manages information concerning said task and action; at least one client machine which enters, outputs and changes information concerning said task and action; and a channel which connects said server machine and said client machine, wherein said at least one client machine can access information concerning said task or action from said server machine, said at least one client machine creates an event rule including an event occurrence point condition expressed by a combination of a title of said task or action and a state transition, an event start condition expressed by a combination of states of said task or action at said event occurrence point and an event execution content expressed by a combination of operations in said task or action with reference to information concerning said task or action memorized in said server machine, said server machine receives and memorizes a plurality of event rules from said at least one client machine through said channel and completes the execution of said task by executing said task in accordance with said plurality of event rules, and wherein said at least one client machine is one of a plurality of client machines handled by users, and each of said users creates said event rules by using a client machine with reference to information concerning said task and action memorized in said server machine.