The article explains why your websites may no longer appear in the search index.

Several circumstances could account for the site not showing in search results. A website may be indexed but may not show up in search results for a particular query. It is also possible that the crawler might not have discovered the site.

To confirm whether or not your site has been indexed, please search for your site using the title and an identifiable unique phrase from the text on your page.

Your site must adhere to the Yahoo! Search Content Quality Guidelines.

It is also possible that the site may have been dropped from the index temporarily. Dropped sites often reappear after an index update. Sites can be dropped for several reasons:

• The site was unavailable at the time of crawling.
• The site structure changed drastically and inadvertently caused problems for our crawler.
• The site accidentally banned the crawler Yahoo! Slurp through a robots.txt file or IP blocking.

In some cases, we may have made an error that caused the site to be dropped accidentally. Please check back in a few weeks. The situation may be temporary in which case the site will appear again after the database has been updated.

If you want a page to appear in Web search results, make sure that page includes some unique text that can be indexed. Pages with no unique text or no text at all may drop out of the index or may never be indexed.

The best way to help the crawler discover your site is to make sure other sites link to your content. To view a list of sites which link to your site, go to the Yahoo! Search box and type: linkdomain:[your website domain name]

For Example:  linkdomain:flickr.com

If you wish to see a list of sites that links to a specific page within your site, go to the Yahoo! Search box and type:  link:[full webpage address]

For Example: link:http://www.whitehouse.gov