When I only got one result from Yahoo! for a search on one of their most popular search terms ("persian kitty"), I looked at the site's html. 'Perhaps these Persian Kitty people have a cunning set of metatags or something', I thought.
Here is the header and <body> tag:
<TITLE> Persian Kitty's Adult Links! </TITLE>
<META http-equiv="PICS-Label" content='(PICS-1.0"http://www.rsac.org/ratingsv01.html" l gen true comment "RSACi North America Server"by "email@example.com" for "http://www.persiankitty.com/" on "1996.04.16T08:15-0500"exp "1997.07.01T08:15-0500" r (n 4 s 0 v 0 l 4))'>
<BODY bgcolor="#ffffff" background="images/pkalbkg.jpg" TEXT="#000000"LINK="#FF00FF" VLINK="#2F4F4F">
Nothing there but a PICS label (and good on them for using it).
Maybe it's those all-important first 250 characters. Some search engines don't index on metatags, they use the first 250 characters instead.
Purrs, claws and curiosity will get you anywhere!
explicit material. If you are offended by such material or are not of sufficient age
to view such material in your jurisdiction, then please click on your
BACK button now to leave here.
Nothing there (not even pictures - I was only interested in the text). Nothing that explains that 'purrfect' result at Yahoo!. OK, so it's not clever html. It could be a unique site, or it could be something in the way that Yahoo! works.