Imagine that you are the parent of two small children and a beaker of milk gets spilt very close to (and splashes over) your shiny new MacBook.
After turning it upside down, shutting it down, removing the battery and wiping away all the obvious spillage you might want to check that there is no liquid inside the machine.
If you were to find yourself in this situation, you might find the ifixit do-it-yourself instructions for Mac and iPod repair very useful (or the Apple Service Source guide for the MacBook).
If you are lucky, it may turn out that the spillage hasn’t made it past the upper cover and into the internal workings of the machine. Phew!