Ok, if you aren't a mapmaker, you shouldn't answer this question. Because you can't.
Here is the question: I was playing around on a Minecraft world. I was wondering if I could make the player detect a certain player's skull under their feet. I did this:
/testforblock ~0 ~-1 ~0 Minecraft: skull 1 {SkullOwner: Notch}
Sadly, this didn't work. Can you try to answer in the most elaborate way?