There have been many changes to the two configuration files required by Struts applications. The web.xml file has had several initialization parameters removed; they are now supported by elements within the struts-config.xml file. The web.xml file also supports a few new parameters. The elements of both files are covered in Chapter 4 and will not be repeated here. You can check the Struts DTD to see exactly which elements are supported in a Struts configuration file.
You will need to update your Struts configuration file to use the latest DTD, which is called struts-config_1_1.dtd. You will get many parsing errors if you forget to do this.