I am trying to download something like www.thissite.com and everything above
and below it in the directory and supposedly staying on the same domain.  I
have several includes and excludes in the parameters (both sites and files).

How can I keep it from downloading every *.pdf and such from external sites? 
The reason is because every now and then it hits a page or external link for
nasa.gov and suddenly there are days and days of downloads of pictures and
files.

Yes, I know I could exclude nasa.gov but the point here is to exclude all
these files from external domains.

Thanks for any help and I hope this question hasn't been asked a hundred times
already.