..The internet does think of the children. And not for their safety, either!

Just avoid Danbooru and most of the boards on 4chan and odd searches/image searches and you should be ok. Oh yeah, and urbandictionary and encyclopediadramatic and most sections of aff.net. Although, if you must visit 4chan, /c/ and /cm/ (cute and cute male) are usually pretty without going into non-worksafe territory. Most fic isn't going to be that hardcore, so if you don't actually go looking for it, you can avoid the darker alleys of the intraweb.