I'm basing this only on the screenshot as I haven't had time to look at the test site. There's not enough contrast between the brownish text and the white background. That's what makes it difficult to read. I think the text should be darker.
You should indeed look at the site, and not take my screenshot as representative.
I am creating this issue a little bit for myself, since I always disable that horrific creation called cleartype (or font-smoothing).
Since many website builders blindly use cleartype, they have no idea how fonts turn out looking on systems without having cleartype enabled.
The situation is even so bad, that there are more and more fonts, designed to look extra good under cleartype, but as a result look extra-horrible without it.
AvikB has taken the trouble to implement a replacement font for all important parts of the site and forum, so a good font is used for systems with cleartype disabled.
Maybe I'll add a screenshot to this post later, to show you how bad some website fonts look on my system.
Even Intel has no clue about this. look at it:
And even a respected IT site as Anandtech don't get it: