It looks like you are using some horribly outdated OS/Browser. If I had to guess, I'd say IE7/8 on Windows XP. For reals?
Arch + xmonad/i3/awesome/whatever no-desktop-compositor-included-DE looks like that out of the box.
Probably other distros, too, but Arch has no font hinting/aa defaults either so the problem is usually exacerbated as compared to something like debian or ubuntu.