It is, literally, a jigsaw puzzle. The top-right piece is fixed in place, so fit the other 5 pieces around this. Then follow the instructions (Click here).
You do not have to put the pieces exactly right, and you don't even have to move any except the one with the question number on it, just click in the circle.
Click the 42nd number 42 (Lol, Hitchhiker's Guide to the Galaxy).
In the Impossible Quiz, click on the 42nd "42" underneath the question.
(see related question)
Click the 42nd 42 (Lol, Hitchhiker's Guide to the Galaxy).
Hover your mouse in the middle right side switch. It's small and hidden. Mouse should react when hovered upon that area.
Click the 42nd 42.
Click the 42nd 42.
42
It is the 42nd 42. Easy XD
you count the 42's until you get to the number 42 you count the 42's until you get to the number 42
Click on the 42nd 42.
42nd 42
the 42nd 42 x
there is not answer, its impossible and the end of the quiz
b
The 42nd one, you silly.
Click the 42nd 42
Click the forty second 42.
Hit the 42nd 42.