1. A data editing apparatus comprising: a database that stores a processing result for each character that constitutes a certain character font set, the processing result being obtained by performing image processing on a raster image of each character to simulate how an image is viewed under a certain visual characteristic; an HTML analysis section for analyzing an HTML document and retrieving processing results for characters corresponding to characters contained in the HTML document from the database; and a modification element locating section for locating an HTML element that needs to be modified in the HTML document, the step of locating being based on the processing results for the characters retrieved by the HTML analysis section, said sections for enabling particular readability of said certain data on a display.