9. A system comprising a set-top box with control circuitry configured to: generate for display a display item having a first program function, wherein the first program function is based on a non-markup language, and the first program function is preprogrammed on the set-top box; receive a markup language document from a remote source; interpret the markup language document to determine that the markup language document assigns a second program function to the display item; update the set-top box based on the markup language document such that the display item has the second program function; and generate for display, the display item having the second program function.
9. A system comprising a set-top box with control circuitry configured to: generate for display a display item having a first program function, wherein the first program function is based on a non-markup language, and the first program function is preprogrammed on the set-top box; receive a markup language document from a remote source; interpret the markup language document to determine that the markup language document assigns a second program function to the display item; update the set-top box based on the markup language document such that the display item has the second program function; and generate for display, the display item having the second program function. 13. The system of claim 9 , wherein updating the set-top box comprises updating a displayed plurality of program listings being displayed in an arrangement by channel to the plurality of program listings being displayed in an arrangement by theme.