Error and Fatal Error

I'm writing a short introduction to XML and would like to have a good example of each of the above that doesn't require too much background knowledge. So far I've covered the basics of a well-formed document, creating elements and attributes. I've shied away from the intricacies of DTDs as they are covered in a separate article. Namespaces are also to be covered later so any examples would preferably be unrelated to either of these two areas.

According to the XML specification a processor may recover from an error that's not described as fatal although in my experience most parsers don't try to do this, would I be wrong here? - and if so what would an example be for something like Saxon or one of the netter known parsers?

Thanks