Complex sentence: The website averaged nearly 20 million visitors per month, according to Nielsen/NetRatings, where around 44% were female, 56% male, and the 12-to 17-year-old age group was dominant.
Split into simpler sentences: The website averaged nearly 20 million visitors per month, according to Nielsen/NetRatings, with around 44% female and 56% male. The 12-to 17-year-old age group was dominant.