Mostly, though, the philosophical underpinnings of pro-ana thought are not quite so Nietzschean. The ''Thin Commandments'' on one site, which appear under a picture of Bugs Bunny smiling his toothy open-mouthed smile, leaning against a mailbox and holding a carrot with one bite taken out of it, include: ''If thou aren't thin, thou aren't attractive''; ''Being thin is more important than being healthy''; ''Thou shall not eat without feeling guilty''; ''Thou shall not eat fattening food without punishing thyself afterward''; and ''Being thin and not eating are signs of true willpower and success.''

The ''Ana Creed'' from the same site begins: ''I believe in Control, the only force mighty enough to bring order into the chaos that is my world. I believe that I am the most vile, worthless and useless person ever to have existed on this planet.''

In fact, to those truly ''in the disorder'' -- a phrase one anonymous ana used to describe it, just as an anonymous alcoholic might describe being in A.A. as being ''in the rooms'' -- pro-ana is something of a misnomer. It suggests the promotion of something, rather than its defense, for reasons either sad or militant. That it is generally understood otherwise and even exploited (''Anorexia: Not just for suicidal teenage white girls anymore'' read the home page of Anorexic Nation, now a disabled site, the real purpose of which was to push diet drugs) is a source of both resentment and secret satisfaction to the true pro-ana community. Its adherents might be vile and worthless, but they are the elite.

The usual elements of most sites are pretty much the same, although the presentation is variable enough to suggest Web mistresses ranging from young women with a fair amount of programming know-how and editorial judgment to angry little girls who want to assert their right to protect an unhealthy behavior in the face of parental opposition and who happen to know a little HTML. But there are usually ''tips'' and ''techniques'' -- on the face of it, the scariest aspect of pro-ana, but in reality, pretty much the same things that both dieters and anorexics have been figuring out on their own for decades. There are ''thinspirational'' quotes -- You can never be too rich or too thin''; ''Hunger hurts but starving works''; ''Nothing tastes as good as thin feels''; ''The thinner, the winner!'' There are ''thinspirational'' photo galleries, usually pretty much the same group of very thin models, actresses and singers -- Jodie Kidd, Kate Moss, Calista Flockhart, Fiona Apple. And at pro-ana's saddest extreme, balancing the militance on the scales of the double-digit goal weight, there are warnings of such severity that they might as well be the beginning of the third canto of Dante's ''Inferno'': ''I am the way into the city of woe. I am the way to a forsaken people. I am the way into eternal sorrow.'' The pro-ana version of which, from one site, is:

Please Note: anorexia is not a diet. Bulimia is not a weight-loss plan. These are dangerous, potentially life-threatening disorders that you cannot choose, catch or learn. If you do not already have an eating disorder, that's wonderful! If you're looking for a new diet, if you want to drop a few pounds to be slimmer or more popular or whatever, if you're generally content with yourself and just want to look a bit better in a bikini, go away. Find a Weight Watchers meeting. Better yet, eat moderate portions of healthy food and go for a walk.

However.

If you are half as emotionally scarred as I am, if you look in the mirror and truly loathe what you see, if your relationships with food and your body are already beyond ''normal'' parameters no matter what you weigh, then come inside. If you're already too far into this to quit, come in and have a look around. I won't tell you to give up what I need to keep hold of myself.

Most of the pro-ana sites also explicitly discourage people under 18 from entering, partly for moral and partly for self-interested reasons. Under pressure from the National Eating Disorders Association, a number of servers shut down the pro-ana sites they were hosting last fall. But obviously, pretty much anyone who wanted to find her way to these sites and into them could do so, irrespective of age. And could find there, as Clairegirl did, a kind of perverse support group, a place where a group of for the most part very unhappy and in some part very angry girls and women come together to support each other in sickness rather than in health.

Then there's chaos -- also her Web name -- who like her friend Futurebird (ditto) runs an established and well-respected pro-E.D. site. Chaos, whom I met in Manhattan although that's not where she lives, is a very smart, very winning, very attractive 23-year-old who has been either bulimic or anorexic since she was 10. Recently she's been bingeing and purging somewhere between 4 and 10 times a week. But when not bingeing, she also practices ''restricting'' -- she doesn't eat in front of people, or in public, or food that isn't sealed, or food that she hasn't prepared herself, or food that isn't one of her ''safe'' foods, which since they are a certain kind of candy and a certain kind of sugar-free gum, is practically all food. (''You're catching on quickly,'' she says, laughing, when this is remarked on.) Also recently, she has been having trouble making herself throw up. ''I think my body's just not wanting to do it right now,'' she says. ''You have the toothbrush trick, and usually I can just hit my stomach in the right spot, or my fingernails will gag me in the right spot. It just depends on what I've eaten. And if that doesn't work, laxis always do.''