check for the below things 1. site:www.yoursite.com - if no result is return you are penalized or de-indexed 2. Keyword ranking - a sudden drop in your keywords. for example from 1st page to 6-10th page 3. Most penalized websites will have page rank as - N/A let me know if you still have any queries on this..,
1. Sudden Google referral traffic drop 2. Huge differences in rankings if you query general search and a single database. 3 Your domain is not #1 for [yourdomain.com] search. 4. [site:yourdomain.com] returns 0 results