Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other pins.
Since my first Arduino-Project I wonder who had the idea of this "glitch" in the pinlayout of almost any arduino-board? Obviously this was done on purpose - but what was the reason behind it? It makes it so difficult to use the arduino on a breadboard or another experimenting-board by just stacking it on top.
Don't be mad for me posting this "stupid" question - but I like to understand!