I'm not sure why, but Safari is disabling subpixel antialising at small font sizes on that page. You can fix it by applying -webkit-font-smoothing: subpixel-antialiased
. See here: http://jsfiddle.net/qLHuc/3/
However, I think you should consider using a heavier font. Have you tested this on Windows? It will likely look very, very light. OSX renders text very heavily when subpixel antialiasing is enabled, and especially heavily when text is against a dark or colored background. What you see in your Safari screenshot is similar to what people who aren't on OSX will see.