This is super useful.

As its creator says, "With mild nudity and the worst excesses of Japan both ending up in the NSFW bin, here's a modest proposal".

(From here.)
Another commenter goes on to expand the system: 

"

• NSFW4 (Cannot Unsee; 2girls1cup, swap.avi)
• NSFW3 (Standard full nudity and sex)
• NSFW2 (Classy nudes, topless, no sex)
• NSFW1 (Close but no cigar, bikini, lingerie, etc)
• SFW (Self explanatory)

     Two additions based on other suggestions:

• NSFW-G (Gore)
• NSFW-L (Language)    

"

I'll try to keep everything here NSFW2 or higher, with a healthy portion of NSFW-L, God fuck it. I'd cut back on NSFW-G if I could but that'd exclude out a great deal of Japanese porn technology, which is an injustice to my readers.

I know why you come here. Don't pretend like you don't enjoy seeing weird shit.