A method in a client-server network, comprising - rendering, by a client, a first webpage for registering a new user, - receiving, at the client, data including personal information and/or indicative of user identity information filled into a second webpage, - submitting the data to a server (2a, 2b, 2c, 2d), - creating, by the server (2a, 2b, 2c, 2d), a user account, - assigning, by the server (2a, 2b, 2c, 2d), a user identification in response to receiving the data, - passing the user identification as a parameter to a third webpage which the user is redirected to, - loading the third webpage that shows a description of tracking and provides a user input in the client for the user to agree to the tracking, - if the user agrees, loading a fourth webpage passing the user identification as a parameter, wherein, on the fourth webpage, the user is informed that an entity tag is set on a browser, - generating, in the client, a setting request for setting the entity tag in the server (2a, 2b, 2c, 2d), - receiving the setting request in the server (2a, 2b, 2c, 2d), - generating the entity tag in the server (2a, 2b, 2c, 2d), the generating comprising providing the user identification in the server (2a, 2b, 2c, 2d) and including the user identification in the entity tag, - generating a response to the setting request in the server (2a, 2b, 2c, 2d), the response comprising the entity tag provided in an entity tag field of the response, - receiving the response in the client, - caching the entity tag in the client, - generating, in the client, a content request for retrieval of content provided in a resource in the client-server network and identified by a resource locator, the generating comprising including the resource locator and the entity tag in the content request, and - transmitting the content request from the client to the resource. - rendering, by a client, a first webpage for registering a new user, - receiving, at the client, data including personal information and/or indicative of user identity information filled into a second webpage, - submitting the data to a server (2a, 2b, 2c, 2d), - creating, by the server (2a, 2b, 2c, 2d), a user account, - assigning, by the server (2a, 2b, 2c, 2d), a user identification in response to receiving the data, - passing the user identification as a parameter to a third webpage which the user is redirected to, - loading the third webpage that shows a description of tracking and provides a user input in the client for the user to agree to the tracking, - if the user agrees, loading a fourth webpage passing the user identification as a parameter, wherein, on the fourth webpage, the user is informed that an entity tag is set on a browser, - generating, in the client, a setting request for setting the entity tag in the server (2a, 2b, 2c, 2d), - receiving the setting request in the server (2a, 2b, 2c, 2d), - generating the entity tag in the server (2a, 2b, 2c, 2d), the generating comprising providing the user identification in the server (2a, 2b, 2c, 2d) and including the user identification in the entity tag, - generating a response to the setting request in the server (2a, 2b, 2c, 2d), the response comprising the entity tag provided in an entity tag field of the response, - receiving the response in the client, - caching the entity tag in the client, - generating, in the client, a content request for retrieval of content provided in a resource in the client-server network and identified by a resource locator, the generating comprising including the resource locator and the entity tag in the content request, and - transmitting the content request from the client to the resource.