If you're unhappy with the way Yahoo! has categorized your products, you can choose the "self-categorization" option in the second step of the feed upload process. To self-categorize, you'll need to add some additional information to your feed or store. Please see instructions at: How do I self-categorize my products?
ProStores Customers:Please note that at this time, self categorization is not available for ProStores advertisers.