> i have used the filter (for example,i exlued
> -*forumslogin* -*feedback* -*math* -*member*
> -*test-centers* -*b-school*)
bad filters

but why? those are keywords of the subsites which I do not want to download. 
eg.
<http://www.manhattangmat.com/forums/gmat-math-f39.html>
<http://www.manhattangmat.com/forums/gmat-prep-math-f30.html>
neither do i want to download threads in those sites.