Which HTTRack version are you using ?Did you modify options in set Options /
Build / Local
Structure Type ?I mirrored a part of the site and have the images in the
correct folders.
In the css, HTTrack resolves url(foo.jpg) as relative to the
folder where the css is which is the case.
I have a few absolute links in a few stylesheets -for
155.css Httrack changes url(back.jpg) into
url(http://csszengarden.com/155/back.jpg)- but as the images
are in the folder 155, removing <http://csszengarden.com/155/>
in 155.css will link the images correctly.
If the images are in the folders, look for http in the css
files, and change absolute links into relatives. Everything
should work then.

Importing the css is a way to hide the style sheet from old
browsers (Netscape 4 and IE 4 in this case). It wouldn't
change anything unless you use an outdated browser.