Demo for my answer: http://stackoverflow.com/questions/8088917/osx-font-width-different-the-windows-for-standard-cross-platform-fonts
Quick demo of my answer to this question: http://stackoverflow.com/questions/8088685/how-can-i-center-a-div-between-floated-divs-with-links-but-still-access-the-link/8088726#8088726