I still got the problem with the image link in an external 
css-file.

I tried to mirror a Lotus Notes Database, all worked fine 
if you add the nsf file extension to the MIME associations 
(to handle it for example like a php page).

But the grabbing of the image from the link of the css-file 
still doesn't work. The whole tag in the css-file is:

.main { background-color:#FFFFFF; background-image:url
('/acims.nsf/back_main.jpg?OpenImageResource'); background-
repeat:no-repeat; background-position:bottom; }