NSFW
 | This article contains PROMOTIONS! Don't say we didn't warn you. |
NSFW means Not Safe For Work. On the majority of the internet, this means images that are even somewhat risque. 4chan, on the other hand, operates under a much more specific definition of NSFW, by which only the presence of nipples or genitals make an image NSFW (although this is not actually an official ruling, it is how the NSFW rules are generally understood and enforced). Everything else is perfectly work-safe. As a result, even 4chan's supposedly "work-safe" boards are plastered with pictures that would give your grandmother a heart attack faster than forcefeeding her an entire loaf of meatbread. And even on those, nipples and genitals make regular appearances, to the joyous cry of "PROMOTIONS!"
On 4chan, work-safe boards have a blue design (known as "burichan") by default, whereas NSFW boards use the standard red/yellow "futaba" colour scheme, as do pages tagged as containing PROMOTIONS on this wiki.