*counter.unexplainable.net/
u can have an invisible hit counter.
It will also tell u abt referrals,visitor's technology,search,enegine keywords etc.Ans yes,it doen not place any kind of ad(neither text link nor image ad!)
I personally use it on my site
www.biologyformhtcet.com-see if u can find it on my page!(remember thar is invisible!)
Forgot to add:Its free!