Validating UTF-8 Encoded Characters in XML Document

Hi,

I have an XML document that is UTF-8 encoded and has the following string "week/xc2/x92s"  When I open this xml file in the Firefox browser, it ignores the UTF-8 encodings, and displays "weeks"  In Microsoft IE, it displays a box in between "week" and "s"  I think the author of the xml document intended to UTF-8 encode the single quote so that it reads "week's" but the UTF-8 encoding sequence is wrong.

I tried using the tool "xmlwf" to tell me if the xml document is valid or not, and it says that it is valid.  So, could this be an issue where the utf-8 encoding sequence is valid, but it is not an actual valid character/symbol?  So, xmlwf doesn't check for the validity of utf-8 characters?  Please let me know if I'm completely off track on this.  Is there an xml validator that will check for the validity of utf-8 characters?

Thanks for your time and help in advance.

Regards,
Monica