Well, child porn should be deleted from the site.
However, the definition of child porn is found in US Code Title 18 Section 2256.
http://www.law.cornell.edu/uscode/718/usc_sec_18_00002256----000-.html
You can read it, but basically, if there is not: sexual activity, beastiality, masturbation, BDSM, or lascivious exhibition of the genitals, it is not child porn. Also, if the picture is pornographic, they have to be over 18; a pornographic picture of a 17 year old is just as illegal as a pornographic picture of a 10 year old.
In other words, if it is a clean picture, G rated, it doesn't matter what age the subject is. It is 100% legal. It is legal to have a picture of a 10 year old girl, genitals completely covered, innocent pose, innocent surroundings.
btw to the 3rd poster above, I probably have more moral authority than you; I have never had sexual contact with anyone, of any age, and I am 33. The opportunity has presented itself a few times, for example, an older woman wanted to take my virginity away when I was in boot camp. But I feel there should be a relationship. No one is interested in a relationship with me, hence I am still a virgin.
And no, I have no intention whatsoever of engaging in sexual activity with a minor. I have every intention of engaging in sexual activity with adults, even more than one adult at the same time, as long as I love them and they love me.
From this moral position, I see no problem with masturbating to a G rated picture, in which the subject is not being abused in any way.
There certainly is no legal problem with it.