Google makes
any word with a  "+" prepended a required wrd in the
 search.  To preclude a word prepend a "-" to it. 
 The latter doesn't work - or at least, it didn't a while ago.  I was
 searching for some music typesetting software called "SMUT".  I'm sure
 you can imagine the false positives; I started adding terms like -pussy
 -beaver to my search to try to suppress them, which simply didn't work.
 And when I reported it to Google, did they fix their bug?  No; they
 added "typesetting" to the list of search targets that suppressed the
 pr0n page hits when searching for "smut" (apparently regardless of the
 search including terms explicitly incidating that the seeker does not
 want them).  They didn't seem to grasp the idea of actually obeying the
 user's stop words, presumably preferring to make users write to the
 directly to be able to find what they're looking for. 
 
If memory serves, Altavista DTRT.
Peace...  Sridhar