Jez123 - 1:03 pm on Sep 17, 2010 (gmt 0)
If you're going to be proactive, then you're first going to need an accurate diagnosis - the root cause. Your sales changes may not even reflect a change in the Google SERPs, you know? And since this thread discusses SERP changes, it's hard for anyone to offer you any insights if you only know the sales changes and not the ranking changes.
Having looked at my stats and assessed the situation this week, these are my guesses at my problem.
I think that either Instant or whatever tweak was made before that went live has diminished some of my important long tail traffic.
Traffic is definitely down but not down so far that I should notice such a change in amounts of orders / enquiries so I can only assume that the quality long tail has been replaced with non quality long tail traffic. Though I don't see that in my stats. Though long tail is very difficult to track and quantify.
My main search term has actually improved from mid to bottom of the first page to number two (probably only temporary rise but I'll take it!). So that tells me there is not a fundamental issue with the site per-se. Also note that that rise has not significantly boosted sales either.
Maybe it's more to do with UK spending and recession (double dip, dare I say it) than google. But who knows.
I think that Tedster is right that it might not be a SERP change though. I certainly can't prove that it is.