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I had 300 good natural links to my site from different sites and site ranked great for my keywords. Somebody (I suppose my competitor) has hacked other sites 2 days ago (checked Google cache) and now Yahoo Site Explorer shows 600 backlinks. I've checked new links - they all are in the same hidden div block - top:-100px; position:absolute;. I'm afraid that Google may penalize my site for these links. I'm contacting webmasters of these sites and their hosting so they remove these links. Is it possible to give Google a notice that these links are not mine so it could just skip them not penalizing me? Is it safe to make "Spam report" regarding links to my own site?