1. An image display device, comprising: a plurality of pixels, each pixel including R, G, and B sub-pixels; a pixel detector to detect a subset of the plurality of pixels as first pixels displaying a still image having constant R, G, and B gray scale values for a predetermined time corresponding a predetermined number of frames, the predetermined number being a natural number greater than one, using an image data supplied from an outside source of the image display device; a gray scale value calculator to calculate average gray scale values of the respective R, G and B sub-pixels of the first pixels displaying the still image for the predetermined time and average gray scale values of corresponding R, G and B sub-pixels of second pixels, the second pixels being included in a predetermined area, the second pixels being adjacent to the first pixels and not displaying the still image, using the image data; a data corrector to correct the R, G and B gray scale values of the first pixels included in the image data, using the calculated average gray scale values of the respective R, G and B sub-pixels of the first pixels and the average gray scale values of the corresponding R, G and B sub-pixels of the second pixels; and a data driver to receive the corrected R, G and B gray scale values of the first pixels, to generate corrected image data with the corrected R, G and B gray scale values of the first pixels, and to supply the corrected image data to each pixel of the plurality of pixels, wherein the data corrector is to generate a scaling variable, using the average gray scale values of the respective R, G and B sub-pixels of the first pixels and the average gray scale values of the corresponding R, G and B sub-pixels of the second pixels, and to correct the R, G and B gray scale values of the first pixels by multiplying the R, G and B gray scale values of the first pixels by the scaling variable, wherein the data corrector is to calculate a positive maximum or minimum value among differences between the average gray scale values of the respective R, G and B sub-pixels of the first pixels and the average gray scale values of the corresponding R, G and B sub-pixels of the second pixels, and wherein the data corrector is to generate the scaling variable by dividing the positive maximum or minimum value by an average gray scale value corresponding to the positive maximum or minimum value among the average gray scale values of the respective R, G and B sub-pixels of the first pixels.