In this css:
<http://1.www.s81c.com/common/v17/css/www_1.css>
httrack saves only some of the referenced images, for some
(left_nav_bullet.png) it even save the image but replace some occurrences of
the url with the local version and some not, example formatted:

this
<code>
#ibm-navigation #ibm-primary-links li ul li
{
  background:none;
  border:0;
  padding-left:7px;
  background:url(//1.www.s81c.com/i/v17/t/left_nav_bullet.png) no-repeat 0
11px;
  background:url(//1.www.s81c.com/i/v17/t/left_nav_bullet.png) no-repeat 0
13px;
  _background:url(//1.www.s81c.com/i/v17/t/left_nav_bullet.png) no-repeat 0
11px;
}
</code>
is replaced with
<code>
#ibm-navigation #ibm-primary-links li ul li
{
  background:none;
  border:0;
  padding-left:7px;
  background:url(../../../i/v17/t/left_nav_bullet.png) no-repeat 0 11px;
  background:url(../../../i/v17/t/left_nav_bullet.png) no-repeat 0 13px;
  _background:url(../../../i/v17/t/left_nav_bullet.png) no-repeat 0 11px;
}
</code>

while this
<code>
{
  background:url(//1.www.s81c.com/i/v17/t/left_nav_bullet.png) no-repeat 0
8px;
  background:url(//1.www.s81c.com/i/v17/t/left_nav_bullet.png) no-repeat 0
11px;
  _background:url(//1.www.s81c.com/i/v17/t/left_nav_bullet.png) no-repeat 0
8px;
  display:block;
  _height:1%;
  padding:1px 4px 1px 7px;
  text-decoration:none;
}
</code>
 remain unchanged


I tried with the default options,

HTTrack3.47+htsswf+htsjava launched on Thu, 25 Apr 2013 10:05:23 at
<http://1.www.s81c.com/common/v17/css/www_1.css> +*.png +*.gif +*.jpg +*.css
+*.js -ad.doubleclick.net/* -mime:application/foobar
(winhttrack -qwC2%Ps2u1%s%uN0%I0p3DaK0H0%kf2A25000%f#f -F "Mozilla/4.5
(compatible; HTTrack 3.0x; Windows 98)" -%F "<!-- Mirrored from %s%s by
HTTrack Website Copier/3.x [XR&CO'2013], %s -->" -%l "en, en, *"
<http://1.www.s81c.com/common/v17/css/www_1.css> -O1 "C:\testcss" +*.png +*.gif
+*.jpg +*.css +*.js -ad.doubleclick.net/* -mime:application/foobar )

, in addition to the ones I normally use, and I tried adding +*.css, +*.png,
+*.gif etc. version 3.47-2.

Of course the problem occurs also when just downloading a site which use this
css.