JBoss: web-app is not bound as a global element

The "Exceptions anyone could have..." series continues with:

web-app is not bound as a global element

Which is a deployment error.

DEPLOYMENTS IN ERROR

The cause was an erroneous web-app declaration in my web.xml file. Here is the correct one:

<web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee
http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

<!-- ... -->

</webapp>

I needed 2.4 to enable EL (Expression Language) by default. Versions 2.3 and lower of the Servlet API ignore EL.