The docs/schema/jboss-web_8_0.xsd file included with WildFly 8.0.0.Final indicates that the schema location is http://www.jboss.org/j2ee/schema/jboss-web_8_0.xsd. However, that URI does not return the schema file but a 404 instead (see http://www.jboss.org/j2ee/schema/ for a listing of the files there).

The file should be hosted where the schema document indicates or the schema should be updated to reflect the proper URI of the schema. Without it third party tools cannot assist in ensuring that the XML is well-formed.