This is a quote that anti-Semites often "dig up" and present to those unfamiliar with Jewish Law as "proof" that Jewish Law condones pedophilia:
Kethuboth 11b : "When a grown-up man has intercourse with a little girl it is nothing."
The subject of discussion is the marital property rights of virgins vs. non-virgins. Virgins have greater entitlements. The rabbis discussed the hypothetical case of a girl raped at an age less than three years old - for the purposes of her rights at marriage, is she considered a virgin or a non-virgin? The answer is that she is considered a virgin. The quotation is out of context - _for the purposes of determining her rights, if a girl less than three has sex with a man, it is nothing. The phrase "it is nothing" is a common Talmudic idiom meaning "it has no bearing on the matter under discussion" (in this case, her property rights at marriage). It does NOT mean "it is perfectly acceptable."
Doreen Ellen Bell-Dotan, Tzfat, Israel