If you download the Icon Set from
http://saratoga-weather.org/carterlake-icons.zip then you don't need the additional icon set (which was only for folks who had installed the set offered from
www.carterlake.org).
The 'fu' icon is the NWS icon for smoke, which in French is fumée ('fu') .. that one had me going for a while too.
The NWS also uses 'smoke.jpg' as the icon for Smoke.
The 'na.jpg' icon is used for 'Not Available' in cases where the digital forecast database is having an issue.
NWS icons and meanings used in their XML feeds are shown at
http://www.weather.gov/xml/current_obs/weather.phpSome of the regions use additional icons (including fu.jpg) for the point-printable and display forecast pages in their region. The carterlake-icons.zip has the superset of the icons used, so should work for all NWS regions.
Best regards,
Ken