view the code of this page, to see how it's used. it works best with dark images. parameters:
- img : URL of the button graphics. the applet-size
should be the same as the picture-size
- himg : URL of the button graphics in mouse-over-state.
- url : URL to link, if used as a button (optional)
- target : name of the target frame (optional)
- size : size of the lighten area (recomended value: 5-30) (optional)