Abstract: A method is provided for preventing delivery of advertising content server device to a client device, where an advertising blocker monitors attempts of the client device to establish a connection to the server device, in the event of a detected attempt to establish a connection, determines if the WebSocket protocol is used for the attempt to establish a connection, if the WebSocket protocol is used for the attempt to establish a connection, checks, for the URI of the attempt to establish a connection, and if the URI may be used to establish a connection, and if the result of the check is that the URI may not be used to establish a connection, ends the attempt to establish a connection. Also provided is a client device for displaying electronic documents, wherein the client device has an advertising blocker designed to implement the method described.