[Zachery]

Originally Posted by StGaensler

I have two things to remark:

As you send a Location: header the Content-type: header doesn't matter as the browser makes a second request for the png file.

This second request takes some time so I suggest doing the "decision" directly on the server without the need of a second request. This only needs the Apache module mod_rewrite:

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule (.*)\.gif$ $1.png [NC,L]

Every non-existing gif file so gets redirected to a png file. I don't check if the png file exists but I think this doesn't matter

Stefan

I don't always replace all of the gif files, so I prefer my version.