a few days ago I observed a sudden drop in many keywords for my site, out of the blue. There's no messages in webmaster tools either and I have retained the same rankings for 12 months+. I am stumped as to why because I have made really no changes to pages and stuff... I had 7 KW in the top 3 drop to zero, 10 KW in top 10 drop to 4, 19 KW in the top 20 drop to only 10 and 21 in the top 20 drop to 12. Has there been any update recently or am I just over reacting?