In my own experiences, Yahoo might be different from Google in it puts more values on on-page seo friendly navigation structure and other on page issues. Have a nice day,
Enhance your on-page optimization, check your broken links, Meta's and other thing that associated with on-page optimization. Also, check your site's speed in loading its another factor.
All Search engines have its own algorithm and when it comes to yahoo it depends on keyword-optimized content in large mass and they do still consider inbound links and other factors.
1. Go to search.yahoo.com 2. type in yahoo SEO techniques ( will come as a suggestion ). 3. read this Yahoo SEO Techniques 4. buy me a beer !