This message comes from the XML-parser and signifies that your web.xml isn't valid, the sub-elements of <web-app> are not defined or in the wrong order. E.g. the <ejb-ref> element you mentioned must be the last sub-element of <web-app>. Check the DTD or use an XML-Editor that validates the document.
Probably your web.xml is not valid against the dtd.
Try to validate it. You can find all the dtds in your jboss directory under docs/dtd or use the official site at http://java.sun.com/dtd
O! thank you!thanks a lot!you are my sun!
it is a ORDER problem.SO STRANGE problem.other AS will not occure this problem.