Online abbreviation for "No problem" as an alternative to You're welcome. I've mostly seen it during my brief foray into Everquest, but I imagine it's widespread in the onlime gamers subculture and elsewhere.

I find it interesting in that it brings the English polite response to Thank you in line with most other languages' response. Most languages have a "No problem" or "It's nothing" way to answer. Of course, I imagine it's used for economy - the less typing, the more time for gaming.