I've noticed that a series of keywords that share the same two-word phrase have completely dropped off Google. They went from between 9-18 to absolutely off the rankings. The odd thing is that the site still ranks for all of it's other keywords as well as ever. I would think that this is purely a page-based penalty, except for the fact that there are a couple keywords that are still ranking well for that same page. So it appears to me that this MIGHT be a keyword-based penalty if there's such a thing. Anyway.... what can I do about a situation like this?