Small dead space on a div button in chrome
CSS. It's because of margin: 10px; on #btn
EDIT
If you use onmousedown rather onclick it will work.
Explaining:
The pseudo class is being activate before the onClick. If you change the values of :active from 2px to 20px. You will see this happening even if you are clicking on the middle of the button.
So after the new values of left and top set by the :active, the mouse isn't on top of the div anymore and can't register the click (press and release).
But onmousedown is still triggered because it doesn't depend on the release of the mouse's button.