http://www.tagesschau.de/ (German news site)
They look good for some time. But suddenly they will be ugly or unreadable with Webfonts. Without Webfonts they look ok.
I should mention that I have the Ghostery Add-on installed. But when I switch it off, the problem occurs also. The fonts are not always unreadable. Often they only change the style after restart of Opera (and deleting cookies, chache & co.), e.g. very small, bold or italic.