Why a Grey Area? Sure, the South Park series and other adult humoured cartoons deserve the 18+ rating, but it's a good website. In fact, it's pretty damn good! Viewer discretion is advised for some shows.
Thewatchcartoononline.com is for both children and adults. Depending on what the person is watching does have mature conduct for certain shows, but other than that it's safe to watch cartoons and anime shows.