Assuming you're referring to the font of the blog's text...

Firefox: Right click, inspect element, click the "fonts" tab on the right.

Chrome: Right click, inspect elmeent, look at "Computed" styles on the right, find Rendered Fonts.

Ironically, the answer is he's not using a font. It uses Times New Roman on my Chrome and DejaVu Serif on my firefox because those are my default system fonts, not because he specified them. If you look at the source of the webpage, you'll see he has zero stylesheet links, all his styles are inline in <style> blocks... So searching font in that one source page is sufficient to find he only styles code blocks, the rest is default.

If you're referring to some other font, I have no clue, sorry!