Type in SEX, DRUGS, and whatever else you can think of along those lines and have a look at what your children are looking at - some ok but most of it not.
youtube is a great site for entertaining . but one bad search and you can see and learn a whole bunch of things you shouldnt know. bad things for little kids
Personally I feel that more could be done to make sure that children don't watch Adult or horrific content. A link to do that is not going to stop them as they can just disable it.