I had a keyword "smoothies†which was ranking on 2[SUP]nd[/SUP] page of google.co.uk, recently that keywords is not ranking anywhere on the SERP of google.co.uk. So do you have any idea what had happened to the keyword ? lovesmoothies.com
Too many variables to give you a correct answer without A. seeing the site and B. knowing your specific backlinking strategy. PM me more info if you would like guidance. It could be your onpage content, keyword stuffing, over optimization. Without seeing the site, I can only make assumptions. Make sure your vary your anchor text and tone the keyword density down if you you suspect its too aggressive.
Google Penguin update was rolled out day before yesterday, you are not alone mate. Millions of users faced the same scenario, best best is to let the dust settle.
Actually KW stuffing can be solved but Making links for the same anchor and if its your main keyword then you can be in this type of problem. Try link diversifying. it can solve the problem.
Yes Google have recently changed search engine coding so that might effect you, so add your site to Google webmaster and add your sitemap, than do a reconsideration and tell them that your website is on plenty issue..
You most likely got hit with the new over - optimization penalty. Try reducing the number of keywords on your pages. Make everything look natural for best results. I did this and my traffic doubled.
I totally agree, i am almost sure this is a case of over optimizing your website, you need to be more careful.