What does this web.xml error mean?

Answer 1

replace

xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd">

with

xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee;http://java.sun.com/xml/ns/j2ee/web-app_2_5.xsd">

The solution is that you have to put semicolon between URLs

I am sure you will not get the error again :)