My site has ranked for 6 to 7 months now on the 1st page but yesterday it moved to 5th to 7th page and fluctuating. I have built several types of links that includes web 2.0's, SB's, forum profiles, and some PBN links but not in an aggressive manner. The site is 2 and half years old already. I tried to research in the forums about this case and some say it could just be a G-Dance, a 'Thin Content Penalty', or an Algorithm-penalty. I didn't enlist my site to the WMT though. Is there any possible way to distinguish if I've gotten a penalty without putting my url to the WMT? Any symptoms or signs if this is just a dance or already a penalty? I am very saddened with what happened to my site as it is my main money site.