I've never heard of 9gag... It's not one of those 4chan style sites, right?
No. It's a meme site, which 4chan is not, it has a far different format and it attracts a far different audience. It's similar in that many of the memes featured on it have also been popular on 4chan in the past, but that's about it. It's also the cancer of the internet.
Oh, goodness.
There is nothing wrong with 4chan as long as you don't mind mutilated penises and not having an apetite for the rest of the day. Especially if you are a sicko.
You won't see any of that stuff if you stay off of /b/, which is widely regarded by other board goers of 4chan to be one of the worst places on the internet.