On the "news"/Photoshopping/discussion website Fark.com, "NSFW" stands for "Not Safe For Work", ie. a link to a website which you should REALLY not click if you are... at work. Or in the public library, or if your small children are present. This usually means nudity or sexual content of some sort, but occasionally includes graphic material of an unpleasant sort, eg. dead bodies. If I understand the rules correctly, posting NSFW pics in the discussion fora is grounds for being banned. Rightly so, as you could get one of the other "Farkers" fired.