The problem is connected with Windows, now I see that you're using the Windows on your iMac, because it impossible to get this problem on MacOS X - it is using system font antyaliasing and fonts looks nice on MacOS X in all apps. Unfortunately we cannot fix it, because it is a problem with the system rendering engine, not with our CSS code. So if the problem is important for you, then you have to use standard fonts instead of the Google WebFonts.