A computer-implemented method for messaging between applications via a web server, the method comprising: receiving, from a web application of a client, an identifier associated with the web application having a subscription to receive selected events associated with a publisher operating on a data network; and receiving, from the publisher, an event notification of at least one of the selected events; characterized in that the method further comprises: determining whether the web application is subscribed to receive the event notification by comparing the received identifier associated with the web application with at least a portion of the event notification, wherein the determining is followed by detecting whether the web application is in a sleep state or an unloaded state; and transmitting, in a case where the web application is subscribed to receive the event notification, an indication of the event notification to the web application, wherein the event notification is provided to the web application via an event page, wherein the event page is an invisible web element which is loaded if an event occurs that is one of a set of events registered by the web application, and unloaded when idle; wherein the event page executes a function related to displaying a pop-up alert with the event notification, wherein the event page provides a callback to a function for retrieving data associated with the event notification, and wherein the transmitting further comprises transmitting, upon receipt of the event notification, a wakeup notification to the web application such that the web application transitions from the sleep state to a wakeup state or from the unloaded state to a loaded state if it is detected that the web application is in the sleep state or in the unloaded state. receiving, from a web application of a client, an identifier associated with the web application having a subscription to receive selected events associated with a publisher operating on a data network; and receiving, from the publisher, an event notification of at least one of the selected events; characterized in that the method further comprises: determining whether the web application is subscribed to receive the event notification by comparing the received identifier associated with the web application with at least a portion of the event notification, wherein the determining is followed by detecting whether the web application is in a sleep state or an unloaded state; and transmitting, in a case where the web application is subscribed to receive the event notification, an indication of the event notification to the web application, wherein the event notification is provided to the web application via an event page, wherein the event page is an invisible web element which is loaded if an event occurs that is one of a set of events registered by the web application, and unloaded when idle; wherein the event page executes a function related to displaying a pop-up alert with the event notification, wherein the event page provides a callback to a function for retrieving data associated with the event notification, and wherein the transmitting further comprises transmitting, upon receipt of the event notification, a wakeup notification to the web application such that the web application transitions from the sleep state to a wakeup state or from the unloaded state to a loaded state if it is detected that the web application is in the sleep state or in the unloaded state. determining whether the web application is subscribed to receive the event notification by comparing the received identifier associated with the web application with at least a portion of the event notification, wherein the determining is followed by detecting whether the web application is in a sleep state or an unloaded state; and transmitting, in a case where the web application is subscribed to receive the event notification, an indication of the event notification to the web application, wherein the event notification is provided to the web application via an event page, wherein the event page is an invisible web element which is loaded if an event occurs that is one of a set of events registered by the web application, and unloaded when idle; wherein the event page executes a function related to displaying a pop-up alert with the event notification, wherein the event page provides a callback to a function for retrieving data associated with the event notification, and wherein the transmitting further comprises transmitting, upon receipt of the event notification, a wakeup notification to the web application such that the web application transitions from the sleep state to a wakeup state or from the unloaded state to a loaded state if it is detected that the web application is in the sleep state or in the unloaded state.