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.
Please put the web.xml here so that we can have a look at it.
If you are using any UNIX/linux box use "xmlwf web.xml" command to check the syntax correctness. In windows you can check it by opening it in IE, it should resolve without any issues or error.
If everything is fine check the tags in between web-app start and end for the app is correctly mentioned and closed.