Simply Button Problem (Teensy 2.0)
You should post a higher quality version next time.

Wiring:

First of all, the button looks like it's not all the way in. Fix that first.

Also, from your picture, it looks like the green wire isn't in the right row:



I can't tell for sure. Also, like mentioned before, you to put the button over the gap between the two sides of the breadboard.

Also, you have a pullup resistor in your circuit and you enable it on the Arduino. And your physical pullup resistor isn't connected to your signal line. And you short your signal line to ground. All of this is incorrect wiring...

If utilizing the internal pullup resistor (like you are in your code), all you should need to do for a circuit is like this:



Just be sure to connect the 5V rail to 5V and the green wire to your digital pin.

Code:

That's all fine. When doing logic with a button, be sure to debounce it.