When accessing a web page on the internet or a file on a local machine, the image file selecting unit selects a plurality of image files to be used for skin generation from a group of image files stored in the temporary storing unit of the browser. The skin image generating unit generates skin images through combination and arrangement of the plurality of selected image files. The update interval setting unit sets an update interval between skin images generated by the image file selecting unit and the skin image file selecting unit and the skin image generating unit.