Disabling and re-enabling the background property does not restore the original background-position values. For example, go to mitzpettel.com and select the sitehead div. Expand the background property under #sitehead, disable it and re-enable it. Note that background-position-x and background-position-y values go from 50% and 100% to initial. This might be a computed style bug, since background-position is not displayed under Computed Style at any time.