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Are you saying that what had been identified by the SEOmoz tools as a valuable link that is on your site is no longer identified as a valuable link? Or has the link on your site itself disappeared? If the link itself has disappeared, you need to investigate with your IT department. If it's that SEOmoz no longer identified the link as strong, send an email to help@seomoz.org and ask our help team about it. Did that help, or did I misunderstand your question?