This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
In the war task you specify the deployment descriptor (web.xml) with an attribute. Also including it as part of the fileset generates the warning. To prevent the warning, exclude the web.xml from the fileset.