It is crucial to understand that Yahoo search results have
several components; Yahoo Categories that match your query; Web
Sites that are in the Yahoo index; and Web Pages that are drawn
from the Google database. Your site may appear in a Yahoo search
and not be in the index!
If your site does not appear under the heading Web Sites, it
isn't in Yahoo. Many people get confused by this. They see their
site appear under Web Pages and think Yahoo has listed them. Not
so!
The reason you want to be in the Yahoo Web Sites index (and not
just Google), is that Yahoo lists these results first when people
do searches. For popular searches, you may have to drill down
through several pages of Web Sites listings before you even see
Google Web Pages results! A decent Web Sites listing in Yahoo
will massively increase your traffic from Yahoo.