Search rankings have been fluctuating even more than usual recently. First we had Yahoo doing a major algorithm change, so they were changing quite a bit. Then we noticed that MSN/Live had dumped most pages from its index and was respidering everything; and of course that meant that rankings disappeared for a few days while it was happening. And then we saw Google weighing in with some noticeable changes. It doesn’t seem to be one of their really big shifts, but a lot of sites seem to have been seeing drops from previously stable high rankings while poorer quality sites have temporarily moved up.
As I’ve said many times in similar circumstances the best thing to do is sit on your hands and do nothing you wouldn’t already be doing. Wait a couple of weeks or so and see what happens. As is usally the case I’m now seeing most of my sites returning to their previous levels, albeit there will inevitably be some datacentres which will reprise the poorer results occasionally until the system clears itself.
There does seem to be more day-to-day flux in Google results than was previously the case, so spot checks once a month are no longer sufficient to see the trends and variations. However at the same time you shouldn’t obsess with constant ranking checks nor should you concentrate on one or two favourite keyword phrases. Look at the whole site profile and remember that there is plenty of traffic to be had in long-tail searches. Those are often better at converting than the big headline phrases which often attract more generic searches that have relatively low conversion rates.