A method for operating an image display apparatus including a display unit, the method comprising: receiving, by the image display apparatus, login information of a first user account associated with a first portable terminal, while a content for viewing is currently displayed on the display unit; logging-in the first user account to the image display apparatus in response to the received login information of the first user account; upon logging-in of the first user account, displaying on the display unit a first screen including the currently displayed content and a per-account content based on a setting of the first user account and, transmitting by the image display apparatus, to the first portable terminal, information required to display the first screen on the first portable terminal; while the first user account is logged-in, receiving by the image display apparatus, login information of a second user account associated with a second portable terminal; logging-in the second user account to the image display apparatus in response to the received login information of the second user account; upon logging-in of the second user account, switching on the display unit the displayed first screen to a common screen and, while the first and second user accounts are logged-in, transmitting by the image display apparatus to: - the first portable terminal, information required to display the first screen on the first portable terminal, - the second portable terminal, information required to display on the second portable terminal a second screen including the currently displayed content and a per-account content based on a setting of the second user account, wherein the common screen is displayed on the display unit without the per-account content for the logged-in first and second user accounts. receiving, by the image display apparatus, login information of a first user account associated with a first portable terminal, while a content for viewing is currently displayed on the display unit; logging-in the first user account to the image display apparatus in response to the received login information of the first user account; upon logging-in of the first user account, displaying on the display unit a first screen including the currently displayed content and a per-account content based on a setting of the first user account and, transmitting by the image display apparatus, to the first portable terminal, information required to display the first screen on the first portable terminal; while the first user account is logged-in, receiving by the image display apparatus, login information of a second user account associated with a second portable terminal; logging-in the second user account to the image display apparatus in response to the received login information of the second user account; upon logging-in of the second user account, switching on the display unit the displayed first screen to a common screen and, while the first and second user accounts are logged-in, transmitting by the image display apparatus to: - the first portable terminal, information required to display the first screen on the first portable terminal, - the second portable terminal, information required to display on the second portable terminal a second screen including the currently displayed content and a per-account content based on a setting of the second user account, - the first portable terminal, information required to display the first screen on the first portable terminal, - the second portable terminal, information required to display on the second portable terminal a second screen including the currently displayed content and a per-account content based on a setting of the second user account, wherein the common screen is displayed on the display unit without the per-account content for the logged-in first and second user accounts.