What does "Mischief Managed" mean?

Search: mischief managed

Why: On Fuck Yeah Tattoos, during Harry Potter week:

This is my “Mischief Managed” tattoo. Obviously I am a Harry Potter nerd. I wanted something unique (or at least somewhat unique) in a sea of HP geek tattoos.

Etc.

I read all the books and saw all the movies, but I don't remember that. It's been a long time.

Answer: It's how you clear the Marauder's Map!

The map is normally disguised as a blank piece of parchment. To view the map, one must tap it with one's wand and recite, "I solemnly swear that I am up to no good." The content of the map will reveal itself.

To hide the contents of the map so the parchment appears blank again, one must again tap it and recite, "Mischief managed."

Source: MischiefManaged.com, Wikipedia, Harry Potter Wikia

The More You Know: F, I need to read all these again. I didn't even remember that the Marauders were Remus (Moony), Peter (Wormtail), Sirius (Padfoot), and James (Prongs).

"Messrs. Moony, Wormtail, Padfoot, and Prongs
Purveyors of Aids to Magical Mischief-Makers
are proud to present
THE MARAUDER'S MAP"

I didn't even remember that Prongs was a name! Uch, I have a lot of work ahead of me.