I have no favicon so I get a lot of 404s, since browsers insist on downloading this little thing. So I created one. Took a social profile photo, croped (Option+K) and played with green colors in Mac’s built-in Preview program. Then, ImageMagick:
$ convert -resize 16×16 dude.png PNG8:favicon16.png
$ convert favicon16.png favicon.ico
FTP. Done. No mo’ 404s for favicon.
Convert images to favicon.