Provo a inserire quello che mi hai consigliato ma non mi valida il
documento XML l'errore č:

cvc-pattern-valid: Value 'error.jsp' is not facet-valid with respect to pattern '/.*' for type 'null'. [16]
cvc-complex-type.2.2: Element 'location' must have no element [children], and the value must be valid. [16]

questo č web.xml
<?xml version="1.0" encoding="UTF-8"?>
<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">
<session-config>
<session-timeout>
30
</session-timeout>
</session-config>
<welcome-file-list>
<welcome-file>
index.jsp
</welcome-file>
</welcome-file-list>

<error-page>
<exception-type>java.lang.Exception</exception-type>
<location>error.jsp </location>
</error-page>

</web-app>