Have you ever seen this?

Published by Chris Coyier

Read Kevin writes in:

A css file will have something like...

background:url(../images/topheader.htm) top left no-repeat;

...where topheader.htm is just an empty file. In this same directory is a jpg named topheader.jpg. How does this work? Why is it done this way?

Yes, I have seen that before. I have no idea how it works or why it's done. I tried to reproduce this technique in my secret laboratory and was unable to get it to work.

I have seen image paths in HTML files point to PHP files before, such as in the old Random Image technique with code like this:

<img src="/path/to/images/rotate.php" />

But that makes sense to me -- the script will return a file path. This is just a blank HTML file...

Is there some kind of server-side scripting going on here? Has anyone else seen this before? Do you know what it's all about?