[ale] Firefox mimetypes

[PairOfTwins]

Anyone:

Why does a fresh install of FireFox 1.0 on Debian, when clicking on a 
jpg attachment via webmail, ONLY offer to save to disk?  Why is "Open 
with" greyed out? 

I've searched ale archives and mozdev, but come up lacking.  In 
desperation, I installed mozplugger and hand edited mozpluggerrc --- and 
still don't get a choice, but at least "display" works as a helper.

Thanks,
Tom