If the content is normal HTML (and not XHTML), then it will most definitely produce broken XML. E.g. the <br> tag has no closing tag in HTML; this will produce broken XML. The solution is to use the CDATA sections as explained by some other poster above.

If you use CDATA sections, then you can also validate your XML files against a DTD or schema, otherwise you would have to describe the complete (X)HTML syntax in your DTD/schema.