I seem to have some kind of penalty on my site. I've been number 1 for my main term for months on end without even dropping one place but now I've suddenly dropped like 50 places for some reason. However when I check webmaster tools it still says I'm number 1 under top search queries..
maybe.... you got too many backlinks in a short period of time (if like this, your SERP will back in one month,likely)
No one of my sites I haven't been doing any link building for in a while. Its been number 1 for months on end and then dropped 50+ places. It certainly wasn't link building.