http://www.ysearchblog.com/archives/000503.html

Has your SEO'd site suddenly dropped in Yahoo for important keywords, while remaining the same on Google.

Like Google, Yahoo actively looks for sites to manually ban or demote. So comments on SEO forums or blogs are probably traced.

Here are a few possible reasons relating to Yahoo's agos. It appears that using link exchange services or linking to bad neighborhoods can have an impact.

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Linking Strategies

   * Link to as many relevant pages as possible. Don't be an island, but at the same time don't link to sites that are not connected to you in any way; this can hurt search engine results. If you link to spam, your ranking could be severely hurt:

   * The pages you link to are the pages your users will link to. Content is king. Create great content and ask yourself if you're a fan of it and if you would link to it.

   * Use descriptive anchor text when linking internally and externally. Use of contextual and descriptive anchor text can have a huge impact on site rankings.

Fighting Spam

   * IP cloaking, keyword stuffing and other spam techniques can draw unwanted attention to your site and potentially reduce your rank or get you removed from specific search engines.

   * Spamming can get you penalized, so even though the site may be retained in the search engine index, rankings may be negatively impacted.

   * While there are a limited number of policemen out there, that doesn't mean they're not actively looking. There are both human and automated ways to detect spam.

TIP:

   * Use Yahoo!'s Dynamic URL Rewriting feature that provides the ability for site owners to alert Yahoo! of the dynamic parameters in URLs that they'd like Yahoo! to ignore; we'll then automatically rewrite accordingly. This will result in more efficient crawl, deeper site coverage and better site ranking due to reduced link fragmentation.