> Here's the site:
> <http://www.vbulletin.com/forum/index.php>
> It's organized like this:
> *.com/forum/forumdisplay.php?forumid=20

Well, first there is a high number of pages - you may 
want to reduce the scope of the mirror - example, 
mirroring the first forum:
<http://www.vbulletin.com/forum/forumdisplay.php?s=aaef9e7a7f716694745c8a383f5e3a82&forumid=1>

Then, define strict filters which only enable 
downloading of threads and associated images:

-* +*.gif +*.jpg +*.png +*.css +*.js 
+www.vbulletin.com/forum/showthread.php*

But, even with these settings, the number of page is 
very high, with many identical pages. The reason lies 
here:

..showthread.php?s=..&threadid=..&goto=nextoldest
..showthread.php?s=..&threadid=..&goto=nextnewest

The reason: many 'next page' and 'previous' page, 
which form different URLs (there is NO way to 'know' 
that <url>id=1&goto=nextpage is the same as <url>id=2)

Therefore, adding:
-*goto=*

will reduce the scope a little more..

With these settings, everything seems to work fine, 
despite the high number of pages.