Can I ask what is wrong?

Friends,

after 12 months of working OK for me, as an enthusiastic adept of external
HTML and CSS validation, I now fail to understand what the CSS Validator is
warning about my web pages.

For example I run www.portalargentino.net/calidad.htm through CSS Validator
and it replies:

----------------------------------------------------------------------------
----
Validator
Error
Target: http://www.portalargentino.net/calidad.htm
Please, validate your XML document first!

Line 36

Column 22

An invalid XML character (Unicode: 0xfa) was found in the element content of
the document.
----------------------------------------------------------------------------
----

There is no Line 36, column 22 in my source HTML file, so I can't know what
to fix.

Can you help me?

Héctor M. Monacci
educa@portalargentino.net y
webmaster@portalargentino.net