Robert_Charlton - 6:07 am on Mar 9, 2013 (gmt 0)
SerpsGuy - When did this drop occur, or was it a series of drops? The information might be helpful in identifying the problem....
Note that up at the top of our Google SEO News home page, we've got a section called...
Google Hot Topics - FAQs
In Hot Topics, right up at the top, we've got a section linking to various types of discussions on Google updates, including not only our monthly Update and SERPs thread, but also Panda Updates and Data Refreshes, etc. I've found these histories, which include dates and descriptions, more useful than similar histories on other SEO sites.
I recommend you take a look at your traffic stats, and see if you can correlate with dates here....
Most Recent Panda Update -
January 22, 2013 [webmasterworld.com]
Google Updates and SERP Changes - March 2013 [webmasterworld.com]
Google Update History [webmasterworld.com]
Panda Iteration Dates [webmasterworld.com]