For years I’ve noticed something odd about websites on a Mac, regardless of the browser used. On OS X, I frequently notice CSS responding differently.
I most often see it visually when the last button is pushed down to the next row in a menu because it’s a pixel too large. Why does this happen?
Example: http://www.dynamicprint.ca/

Try to update your css with below css rules and you will see the problem is gone.
http://www.dynamicprint.ca/ (line 81)
SS: