The Google Slump strikes!
Oh dear, I knew things were going too well!
The number of pages Google has indexed has been steadily gorwing, from 400 a few weeks ago to 20,000 last week to (as of yesterday) 48,200. My visitor numbers had also been steadily growing in response to this and, with adsense now optimised on the site to the best of my current ability, my click-through-rate and revenue had been increasing rather nicely.
...and then Bang!
Looking at the stats for the last 3 days, my visitor numbers have been dropping for the first time since launch - currently down around 65% from the peak. This seems very odd, but I notice many others have experienced the same phenomenon.
Having racked my brain, the possible reasons for this slump could be:
1) At the end of last week I redesigned the front page to include more category links as these seemed to be the ones that Google ranks most highly, and those correlated closely with the search terms bringing people to the site.
2) I also disabled my sitemaps as they appeared to be interferring with my stats (although that is probably nonsense).
3) The site was down for a few hours on Monday whilst I was out (Mr Sod and his damn law at work again) which did not go unnoticed by the google sitemap reports (which carry on working, even with no sitemaps listed!).
To get things going again (hopefully) I have reinclude the sitemaps and made provision to reduce the chances of the site going down again (the problem appeared to be a scarcity of disk space and java memory).
The main lesson to come out of this is to be patient. Changes to the site can take weeks to be finally reflected in Google's index so tweaking the site in future needs to be done in small stages, measuring the impact contnuously until things settle down before making the next change.
I will now sit tight to see what happens in the next few weeks.