logo filename in the example

error message when this does not work

of the formats (so far, html, html3, bbfr, and svg)

sometimes send them to external viewers and become confused if the
filename ends in '.php' (despite our correct content-type!)

script might be content-negotiated, renamed, symlinked, or otherwise
alised in URI-space.

lynx/elinks) and some alt="..." text so the validator does not complain.