The site spotted the poster at a local movie theatre and took a picture of it. In fact, the one-sheet is a 3D lenticular poster:
This was up on display at my local movie theater (where I went down to watch the The Dark Knight IMAX short for the second time) and looks pretty incredible in person. The helmet under his arm pops outwards towards you, whereas the car is set in the background but is also 3D. The look when you pass by is actually very cool.
Take a look at the poster below (although the photo-quality is not great!).
Speed Racer arrives in theatres on May 9.