This could not be a more perfect motto. The content on Newgrounds ranges from cutesy games for preschoolers to hardcore pornography and, for example, two violent videos by a school shooter that were uploaded before the shooting. There are plenty of squeaky-clean cartoons and games here, but much of the content on the site - including the flash created by Tom Fulp himself - is extremely offensive, making fun of school shootings, rape, 9/11, murder, racism, pedophilia, and so on. Newgrounds was the birthplace of "V-Tech Massacre", if it gives you any idea. There is an entire section devoted to flash that deliberately tries to be as offensive as possible, making fun of recent tragedies. I used to frequent this website when I was younger, and I was very disturbed by much of the content on it. This is the 4chan of flash. You have been warned.
What other families should know
Too much violence
Too much sex
Too much swearing
Too much consumerism
Too much drinking/drugs/smoking
Safety and privacy concerns