Sgt_Kickaxe - 8:00 am on Feb 3, 2013 (gmt 0)
Established content? I've noticed that a page can remain untouched for the longest time and stay steady in rankings but the moment you make a small change(like add tracking) the old rankings can be lost. I wonder if pages are sometimes exempt to new Google changes if they haven't been modified in some time. These pages might get re-evaluated under current guidelines only when they are modified.
Just a theory.