Thanks for the feedback. I just fixed it.
http://i.imgur.com/Xu13n7j.png
The typophiles here will surely yell at me for getting the terminology wrong, but my experience is that fonts are heavier on OS X and whenever I see a site with whisper-thin text like the above I suspect it was tested on OS X only.
Edit: removing the font-weight CSS attribute makes the page legible. The issue is that you specified a font-weight under 400 ("normal"), and different font engines snap in different ways.
It’s just bad design.