This article explains that you need to contact the website owner or webmaster to have personal information removed.

Yahoo! Search reflects content throughout the Internet and is built from billions of documents on websites around the world. Our primary goal is to provide quick, intuitive access to the wide variety of information available on the Web. The search results you see are links to content that has originally been published elsewhere.

If a website has published your personal information or incorrect information about you, you should contact the site owner or site content provider to have that information corrected. Yahoo! does not control and is not responsible for such content.

Note: When providing personal data to a website, be sure to check the site's privacy policy. In some cases, your submission to a site grants them permission to publish that information.

After the site has removed or corrected the published content, the information in the search database is corrected by normal content refresh processes. You might still see the pages listed in the database for some time after the site content or control documents are changed. The changes take effect in the search database when the information is updated in our next refresh cycle. On average, this takes place more than once a month.

Note: Often, personal names are not unique, and multiple people have the same name. Pages containing content about a different person with the same name might not be subject to suppression.