1. An image display apparatus for processing externally acquired display data and displaying an image based on the processed display data, wherein the image display apparatus is a computer-embedded digital television, comprising: a basic function program storage section intrinsically storing a plurality of basic function programs each of which executes one basic function, wherein the plurality of basic function programs are not changed by user operation on the digital television; a display data receiving section receiving the display data from an external device via Internet, the display data containing the image and a control script that defines at least a first function of displaying the image, wherein the first function defines the layout of the image; and a processor operably performing as: a basic function executing section for executing one or more of the plurality of basic function programs as called directly from the control script, the basic function programs being stored in the basic function program storage section; and a control script executing section for controlling the basic function executing section according to the control script so as to perform the first function being defined by the control script, wherein the control script execution section is not a part of an Internet browser; the control script further defines a second function which the image display apparatus performs in response to an event that occurs in the image display apparatus while the image is being displayed by the first function, the control script executing section controls the basic function executing section according to the control script so as to execute the second function, the first function and the second function are defined by the control script as a combination of basic functions stored in the basic function program storage section, and the first and second functions are operationally redefinable as different combinations of the intrinsically stored basic functions, by changing the control script.