XML Problem

Hai guy...
I;m a Noob here, and I need your mentoring...
In got a problem with my webservice, it's displaying error message like this :
XML Parsing Error: prefix not bound to a namespace
Location: file:///I:/TRX%20Keu%20SIAK/reversal.xml
Line Number 4, Column 4:

Can somebody give tutorial for this

Thank you very much

It looks to me like you have some invalid XML somewhere. But it is hard to say exactly where without knowing more about your code. Is this already useful?

Alex