The application relates to a method for determining page impression in a client-server system, the method comprising opening a page in a browser running on a client device provided in the client-server system, starting an application in the browser in response to the opening of the webpage, establishing a persistent connection between the web browser on the client device and a server device provided in the client-server system, storing first electronic information in the server device, the first information indicating a start time for establishing the persistent connection, keeping the persistent connection, in the server device, receiving termination information indicating termination of the persistent connection, storing second electronic information in the server device, the second information indicating an end time for terminating the persistent connection, and determining an opening or presentation time from the first and second electronic information, the opening or presentation time indicating the time between opening and terminating of the page in the browser.