Quoting: Hounds
ah, interesting. that perhaps explains the hand-held at the gym telling me i was steadily increasing body fat while dropping poundage and working out religously over a three week period...
That'd be a huge red alert to me, losing weight but having your body fat % go up is an indication that you've been training too hard and your body is sacrificing muscle to make itself more energy-efficient (think of your body going green, but in a bad way). This isn't necessarily the case for you though, seeing as how you're measuring in the middle of the day so there are several different factors that can affect the measurement, for example hydration, diet, caffeine intake, etc.
Best to do it first thing in the morning so you can be consistent about as many of those variables as possible. There's still going to be fluctuation of course, but I tend to find that the numbers are the most "honest" with me then.
Itadaki's link was interesting to look at, but just to further emphasize a point that guy alludes to in his descriptions: everybodies body is different in terms of appearance; I know folks who are at 13% body fat that don't look as cut in areas as guys who are 18ish because of the way their body distributes fat.
Oh, and just to repeat the excellent point brought up earlier, because it is so important that it can never be said often enough: the actual number doesn't matter, as long as it's going down over time.