So, the same remarkably clever person/group behind the hilarious signs on the out-of-service Marshak elevators [see here] have struck again. This time, with a large sign, duplicated on this website: http://marshakelevators.com/404/
I've taken a screenshot of the 404 in case they take down that site, but in the meantime, check it out there, and be sure to click on those links!
From the comments on that site, it's unclear who exactly is behind the signs. Maybe CCNY's administration is funnier than people have given them credit for.