Tomcat fails to load a JSP page or servlet which refers to classes from xml-
apis.jar located in the WEB-INF/lib directory of the webapp.

Error message:
javax.servlet.ServletException: javax/xml/transform/URIResolver
...
root cause 

java.lang.NoClassDefFoundError: javax/xml/transform/URIResolver
...

(see full stack trace in attachment)

This is the contents of a sample webapp that produces the problem:
webapps\
  test\
    index.jsp         (see attachment)
    WEB-INF\
      lib\
        xalan.jar     (version 2.2.D13)
        xerces.jar    (version 1.4.4)
        xml-apis.jar  (from xalan dist)

Running such an webapp in Tomcat 3.3 does not cause any problems.

Although putting xalan.jar and xml-apis.jar into the common/lib directory 
solves the problem, this is very inconvenient because the webapp(.war) should 
be self-contained.