Hi Robert,
I assume you are serving the files using a simple link - ie something the user clicks on with an href that points to the file?
Also I presume you are able to identify the file type from the name or path?
If so, there is a method in WebHandler (the parent method is in nethttp.clw) called _GetContentType.
It takes a name as a parameter, and from that name you return a string containing the content type.
Note that the filename can include any parameters passed, so if you are basing your code on the extension, you need to strip the parameters off first. A quick look in nethttp.clw will give you the idea.
So you can add code to WebHandler, before the parent call, to add in custom types.
Cheers
Bruce