content type headers

Hi, 

I've got some old code to deal with and I have hit a problem. 

If there is a request for a page that has mixed content EG: 'text/html' 
and 'image/jpeg', the image media is not being displayed correctly under 
the FireFox browser. 

The way things currently work is that media other than text/html is 
output from a separate page, so you might have a bit of html that for an 
image that looks like this:

<img src="/images/showImage.html?imageid=123456" alt="" />

Within showImage.html you have a 1) a piece of code that supposedly sets 
the content_type to image/jpeg, and 2) calls to a function that 
literally prints the image based on is CGI param 'imageid'.

In my experiments, IE is correctly identifying the media and Firefox is 
not. However I think FF is expecting the content_type to be sent with 
the media and IE is guess* based upon the media it receives.

So my question, initially, is can a request set the content_type more 
than once?

Thanx,
Dp.