As Google penalizes sites for selling text links and huge pagerank drops are being reported widely on top sites (we also dropped from PR6 to PR3, with no paid text links!), you can file a Reconsideration Request to Google if you believe you do not sell text links and your site is compatible with Google webmaster guidelines.
The Google Webmaster tools is an excellent official resource for webmaster interaction with Google. If you have never signed up there, you must verify your site. Therein is a form to submit a reconsideration request.
Request reconsideration of a site only when it has violated the webmaster guidelines, since by submitting this form, you acknowledge that your site violated Google quality guidelines in the past, and now you have fixed the issue and it no longer violates Google’s quality guidelines. Then have some patience and wait several weeks for the re-evaluation process. Also note that they will not reply individually to reconsideration requests.
If you pagerank has dropped by mistake, this seems to be the only official way to contact Google. Try it … it might work!
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