Slightly o/t: Does the font on his site look awful to anyone else? In opera, the site looks like this for me, which is horrible. I have to mash the readability script bookmarklet to read it: http://imgur.com/ODnjY.png
But yes, I have the same problem. I'm using Opera too, and use shift+g to disable stylesheets when reading that page. (You need to enable single-key shortcuts for this to work)
The screen shot you posted doesn't obviously match any of the listed fonts, but if you can find your OS's list of installed fonts, just check which of those you have installed.
It's kind of bizarre that you're defaulting to an italic font when the site doesn't seem to request italic, it may be that you have only the italic variant of some font installed.
Seems to be Palatino Linotype (that's the first one of the font-family my OS has available). Not sure why Opera has decided to italicise it though, as the installed font looks fine normally.
Palatino being a pre-computer font also has a tendency to be hurt by screen aliasing a lot. If you can activate some sort of anti-aliasing/smooth font layer on your computer even the italicized version shouldn't look so painful.
