i am using msdn sample code and it has jsonp wrapper files you can find the code here
of this article and MSDN article JSON with Padding (AJAX)
but when i run the code it throw me this error:
Encountered invalid root element name 'HTML'. 'root' is the only allowed root element name
what does it mean?

It means that you’ve made some kind of web request that is expecting to get some kind of XML data back but instead it is getting HTML data back. The usual cause is a messed up URL. If your URL were correct, then XML would be returned as expected. Since it is messed up you end up getting back HTML (probably an error page at that).
Check your URLs to make sure they are correct.