QUOTE(Jill @ Feb 9 2005, 08:54 AM)
(These are the kinds of things people notice when they check results too often; the stuff they'd never notice if they didn't check much because it might be missing for one minute, but back the next.)
Not necessarily from checking too often, if the glitch is there for a few days and the page that is missing previously ranked well for some high-volume phrases. Same thing happened to me...I noticed a drop in traffic, got to rooting around in the log files, and figured out "www.mydomain.com" was missing. Google did work itself out and things returned to normal.
We figured the temporary glitch was probably somehow related to bots not recognizing "www" and "non-www" as same page, combined with temporary hiccup in the algo. If you want to look more into the technicalities of that, the Permanent 301 Redirect
thread is a good resource. When you get to Ron's long post, if you are not already familiar with what he's saying, be sure to read the whole thing...first time through I stopped in the middle and got messed up!