CSS validator reports error in XML

When I one of my pages (http://www2.arnes.si/~sopjsimo/translator.html)
through CSS validator, it reports error in XML, and that I should
validate XML first. However, W3C HTML validation service reports no
errors on that page
(http://validator.w3.org/check?uri=http%3A%2F%2Fwww2.arnes.si%2F%7Esopjsimo%2Ftranslator.html&charset=%28detect+automatically%29&doctype=%28detect+automatically%29)

I don't see any error at the reported position either. What's wrong?

-- 
Jernej Simoncic, jernej.simoncic@guest.arnes.si
http://www2.arnes.si/~sopjsimo/
ICQ: 26266467

They can't hit it while I'm standing here holding it.
       -- Lefty Gomez's Principle of Productive Procrastination