A method of a server system communicating with a client system. The method includes a passive system monitoring network traffic between the client-server system. The server sending a page response including an agent, e.g., a Javascript that becomes operable on the client system. The agent monitors events on the client side, e.g., DOM events, and communicates these to the server side. A set of rules that define prescribed user events are maintained by the passive system and applied to the monitored network traffic to determine whether a prescribed user event occurred. Responsive to the prescribed user event occurring, an asynchronous message is generated and sent to the agent in response to a received DOM event message, the asynchronous message comprising a command to be executed by the agent to alter the users web application flow at the client in a manner that is substantially transparent to the web application.