A method of operating an image display apparatus comprising: receiving a first video signal; generating a first image based on the first video signal; receiving a second video signal; generating a first thumbnail image based on the second video signal; displaying simultaneously the first image based on the first video signal and a first thumbnail list including at least the first thumbnail image in a compact-view mode; - generating a second thumbnail image based on the second video signal to update the first thumbnail image; - determining whether an error is detected in the second thumbnail image; - if an error is detected and an error ratio of the second thumbnail image is less than a reference value, displaying the second thumbnail image instead of the first thumbnail image in an updated first thumbnail list; - displaying, according to a user input, a second thumbnail list including a plurality of thumbnail images including the first thumbnail image or the second thumbnail image in a full-view mode on the entire display, wherein the reference value is set differently for the compact-view mode and the full-view mode, and wherein the size of thumbnail images displayed in the full view-mode is greater than the size of thumbnail images in the compact-view mode; wherein the error includes at least one of size error, syntax error, checksum error, continuity error, or content error of the thumbnail image; and wherein the error ratio of the second thumbnail image indicates a ratio of a size of erroneous part of the second thumbnail image to a size of the whole second thumbnail image. receiving a first video signal; generating a first image based on the first video signal; receiving a second video signal; generating a first thumbnail image based on the second video signal; displaying simultaneously the first image based on the first video signal and a first thumbnail list including at least the first thumbnail image in a compact-view mode; - generating a second thumbnail image based on the second video signal to update the first thumbnail image; - determining whether an error is detected in the second thumbnail image; - if an error is detected and an error ratio of the second thumbnail image is less than a reference value, displaying the second thumbnail image instead of the first thumbnail image in an updated first thumbnail list; - displaying, according to a user input, a second thumbnail list including a plurality of thumbnail images including the first thumbnail image or the second thumbnail image in a full-view mode on the entire display, - generating a second thumbnail image based on the second video signal to update the first thumbnail image; - determining whether an error is detected in the second thumbnail image; - if an error is detected and an error ratio of the second thumbnail image is less than a reference value, displaying the second thumbnail image instead of the first thumbnail image in an updated first thumbnail list; - displaying, according to a user input, a second thumbnail list including a plurality of thumbnail images including the first thumbnail image or the second thumbnail image in a full-view mode on the entire display, wherein the reference value is set differently for the compact-view mode and the full-view mode, and wherein the size of thumbnail images displayed in the full view-mode is greater than the size of thumbnail images in the compact-view mode; wherein the error includes at least one of size error, syntax error, checksum error, continuity error, or content error of the thumbnail image; and wherein the error ratio of the second thumbnail image indicates a ratio of a size of erroneous part of the second thumbnail image to a size of the whole second thumbnail image.