Method for authenticating a user, which method comprises the steps of a) providing a central server, in communication with at least one authentication service provider (110,120,130), arranged to authenticate users via a respective authentication web interface, and at least one user service provider, arranged to provide user services to users via a respective user service web interface; b) providing, for a particular user and using a web browser executed from or by a particular electronic device (170,180), access to the authentication web interface, and upon an authentication of the user by each one of said at least one authentication service provider causing the authentication web interface to allow the central server to place a respective cookie on the particular electronic device identifying each respective authentication service provider, of the at least one authentication service provider; c) providing, for the user and using the same web browser executed from the same particular electronic device, access to the user service web interface, and as a result of providing access to the user service web interface, providing several cookies, wherein said several cookies consisting of said placed respective cookie identifying said each respective authentication service provider of the at least one authentication service provider, to the central server; d) causing the central server to identify, based upon the said several cookies provided to it, the authentication service provider; e) causing, based on step d), the web browser to be redirected to the authentication service provider; f) causing based on step e), the authentication service provider to authenticate the user; and g) causing based on step f) user authentication information to be provided to the user service provider, wherein in step c), said several cookies that have been placed by the central server in step b), associated with several respective authentication service providers (110,120,130) are provided to the central server, and in that, in step d), the central server determines a minimum allowable authentication security level for authenticating the user and selects one authentication service provider, being associated with at least one authentication security level which is at least as high as said minimum allowable authentication security level, from the several authentication service providers as identified using the said cookies. a) providing a central server, in communication with at least one authentication service provider (110,120,130), arranged to authenticate users via a respective authentication web interface, and at least one user service provider, arranged to provide user services to users via a respective user service web interface; b) providing, for a particular user and using a web browser executed from or by a particular electronic device (170,180), access to the authentication web interface, and upon an authentication of the user by each one of said at least one authentication service provider causing the authentication web interface to allow the central server to place a respective cookie on the particular electronic device identifying each respective authentication service provider, of the at least one authentication service provider; c) providing, for the user and using the same web browser executed from the same particular electronic device, access to the user service web interface, and as a result of providing access to the user service web interface, providing several cookies, wherein said several cookies consisting of said placed respective cookie identifying said each respective authentication service provider of the at least one authentication service provider, to the central server; d) causing the central server to identify, based upon the said several cookies provided to it, the authentication service provider; e) causing, based on step d), the web browser to be redirected to the authentication service provider; f) causing based on step e), the authentication service provider to authenticate the user; and g) causing based on step f) user authentication information to be provided to the user service provider, wherein in step c), said several cookies that have been placed by the central server in step b), associated with several respective authentication service providers (110,120,130) are provided to the central server, and in that, in step d), the central server determines a minimum allowable authentication security level for authenticating the user and selects one authentication service provider, being associated with at least one authentication security level which is at least as high as said minimum allowable authentication security level, from the several authentication service providers as identified using the said cookies.