I just had another strange behaviour:
If I remove the registering of the default-servlet with mapping to "/" in webdefault.xml of jbossweb.sar the stylesheets and pictures for my other servlets will not be found when addressed correctly with the servlet-path...
Ok, I managed it with some workaround...
Due to JBoss being an application-server and not a web-server I created a dummy web-application-archive with all needed files except a real servlet and registered it with the welcome-file index.html to the "/"-context.
The index.html has the meta-equiv-tag to refresh to my desired default-url...
If there is any way to do this more easily with configuration any hint is appreciated.